'She's the toughest opponent I've ever played in my life': Serena Williams is gracious in historic US Open clash victory against sister Venus... and now just two games away from the Calendar Grand Slam

• Serena now heads to the quarter-finals after beating Venus 6-2, 1-6, 6-3
• Serena will now face Roberta Vinci in the semifinals 
• Siblings played each other for the 27th time at Flushing Meadows on Tuesday night
• Serena ousted fellow American Madison Keys 6-3 6-3 and Venus thrashed Estonian qualifier Anett Kontaveit 6-2 6-1
• Serena previously won eight of the pair's last 10 major battles
• She first beat her big sister in 2003 by winning the grand slam season-opening Australian Open 
• Among the celebrities in the crowd were Oprah Winfrey, Donald Trump, Kim Kardashian and Kendall Jenner

World No. 1 Serena Williams continued her path to a calendar-year grand slam title after beating out big sister Venus Williams tonight in a compelling U.S. Open quarter-final.

With sports pundits commenting it was the strongest game from Venus in recent memory - breaking her sister twice in the second set - Serena recovered her strength and came out on top 6-2, 1-6, 6-3.

'It's a really great moment,' Serena said during an on-court interview with ESPN's Mary Joe Fernandez.

'She's the toughest opponent I've ever played in my life and the best person I know. It's going against your best friend and at the same time going against the greatest competitior in women's tennis.'

'When I'm playing her I don't think of her as my sister. When you're in the moment you don't really think about it. We trained all our lives to play on this court and on this stage in front of you guys. It's a great honor.'

'She came out hitting so hard. I was on defense a lot because she has so much power. It wasn't really easy today at all.'

'This is a big moment for both Venus and I. We both had a chance to be in the semi-finals. It's a grand slam. We're very competitive. We're just trying to give each other a great match.' 

She did it: Serena Williams reacts after defeating her sister and compatriot Venus Williams in their quarterfinals match at the U.S. Open

Celebration: At nearly 34 Serena is now two matches away from becoming the fourth woman to do
the calendar year Grand Slam

Venus Williams  hugs sister Serena Williams after their match on day nine of the 2015 U.S. Open tennis tournament on Tuesday

Serena Williamshugs Venus Williams after winning their quarterfinal match at the U.S. Open tennis tournament on Tuesday in New York

Historic match: Serena Williams, 33 (right), is three wins away from recording the first calendar Grand Slam in 27 years and cementing her place as the greatest women's tennis player of all time, but first she must beat sister Venus, 35, (left), tonight in their 27th career meeting

Serena Williams returns a shot to sister Venus during a quarterfinal match at the U.S. Open tennis tournament on Tuesday night

Venus, whose last slam triumph came at the 2008 Wimbledon, said she thought she was playing well enough to win her third U.S. Open title

Serena Williams returns a shot to sister and compatriot Venus Williams during their quarterfinals match at the U.S. Open Championships

Serena Williams of the United States reacts against Venus Williams during their Women's Singles Quarterfinals match on Day Nine of the 2015 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2015

Celeb support: Oprah Winfrey, left, and Gayle King watch a quarterfinal match between Serena Williams and Venus Williams

Republican presidential candidate Donald Trump and his wife Melania watch a quarterfinal match between Serena and Venus Williams

Donald Trump shakes hands with US teennis great John McEnroe as Venus Williams plays Serena Williams during their quarterfinals match

Kim Kardashian and Kendall Jenner in the stands of Venus Williams and Serena Williams quarterfinals match on the ninth day of the 2015 US Open Tennis Championship

Serena Williams reacts after losing a point to Venus Williams during a quarterfinal match at the U.S. Open tennis tournament

Gearing up: Serena and Venus Williams pose for a photo before playing each other in a quarterfinal match at the U.S. Open 

Historic match: Serena Williams, 33 (right), is two wins away from recording the first calendar Grand Slam in 27 years and cementing her place as the greatest women's tennis player of all time, after beating sister Venus, 35, (left), tonight in their 27th career meeting

After wins at the Australian, French and Wimbledon, Serena is now just two victories from joining the exclusive club whose short membership list includes Maureen Connolly, Margaret Court and Steffi Graf.

HEAD-TO-HEAD: THE HISTORY OF SERENA VS. VENUS 

1998 Australian Open - Venus won 7-6 6-1 
1998 Rome - Venus won 6-4 6-2 
1999 Miami - Venus won 6-1 4-6 6-4 
1999 Munich - Serena won 6-1 3-6 6-3 
2000 Wimbledon - Venus won 6-2 7-6(3) 
2001 U.S. Open - Venus won 6-2 6-4 
2002 Miami - Serena won 6-2 6-2 
2002 French Open - Serena won 7-5 6-3 
2002 Wimbledon - Serena won 7-6(4) 6-3 
2002 U.S. Open - Serena won 6-4 6-3 
2003 Australian Open - Serena won 7-6(4) 3-6 6-4 
2003 Wimbledon - Serena won 4-6 6-4 6-2 
2005 Miami - Venus won 6-1 7-6(8) 
2005 U.S. Open - Serena won 7-6(5) 6-2 
2008 Bangalore - Serena won 6-3 3-6 7-6(4) 
2008 Wimbledon - Venus won 7-5 6-4 
2008 U.S. Open - Serena won 7-6(6) 7-6(7) 
2008 Doha - Venus won 5-7 6-1 6-0 
2009 Dubai - Venus won 6-1 2-6 7-6(3) 
2009 Miami - Serena won 6-4 3-6 6-3 
2009 Wimbledon - Serena won 7-6(3) 6-2 
2009 Doha - Serena won 5-7 6-4 7-6(4) 
2009 Doha - Serena won 6-2 7-6(4) 
2013 Charleston - Serena won 6-1 6-2 
2014 Montreal - Venus won 6-7(2) 6-2 6-3 
2015 Wimbledon - Serena won 6-4 6-3

The last player to accomplish a calendar-year Grand Slam was Graf in 1988. 

Nabbing the title would cement Serena's place as the greatest women's tennis player of all time. 

'I think people love to see history being made,' said Venus following her fourth-round win over Estonian Anett Kontaveit on Sunday. 

Certainly there are no secrets between the sisters who will have been playing each other since they were first handed rackets growing up in the hard-scrabble Los Angeles Compton neighborhood and began an unlikely and inspiring journey to the top of their sport.

As professionals they had - before Tuesday - clashed 26 times with Serena holding the advantage 15-11.

Serena won their last meeting in July at Wimbledon while Venus came out on top when they last met on a hardcourt last August in Montreal.

In grand slams Serena also holds the advantage 8-5 and 6-2 when they have met in the final.

Serena maintains Venus has always been her toughest opponent and with 11 losses to older sister, nobody has beaten the 21-times grand slam winner more.

Retired Jennifer Captriati comes the next closet with a 10-7 record while Justine Henin (8-6) and Martina Hingis (7-6) each had six wins.

Only a handful of players can claim more than one career win over the muscular American and only two, Belinda Bencic and Petra Kvitova, have beaten her this season.

'I mean, I'm playing, for me, the best player (Venus) in the tournament and that's never easy,' said Serena, 33, who is two years younger than Venus.

'She's beaten me so many times. I've taken a lot of losses off of her -- more than anybody.

'She's a player that knows how to win, knows how to beat me, and knows my weaknesses better than anyone ... the only player in the draw I don't want to play, not only because she's my sister, but for me she's the best player.'

It was 18 years ago that Venus reached the U.S. Open final for the first time but Serena lifted the family's first grand slam trophy when she won two years later at Flushing Meadows.

While Serena has long looked up to big sister and credits her with much of her own success she long ago stepped out from Venus's shadow to become one of the sport's all-time greats.

Whenever the Williams sisters clash on court it is a major tennis event and Tuesday's meeting is ripe with drama and suspense.

Two of the sport's dominant figures, the sisters long ago accepted the inevitable that they would stand across the net blocking each other's path to a title.

The matches have not always produced riveting tennis but over the years the angst has eased, at least making the contests more enjoyable for the sisters if not the fans.

'Nowadays, I would agree, I think it's more fun than it used to be,' said Serena following her fourth-round win over Madison Keys. 'We really relish the opportunity. We're both happy to still be involved in getting so far.

'And it's still super intense. She's doing well and she wants to win this. So do I. It's not easy.

'I think it's been an amazing rivalry. I think it's meant a lot. We've done a lot for the sport. I think, you know, hopefully it can continue as long as we play.'

Kim Kardashian arrives to watch a quarterfinal match between Serena Williams and Venus Williams at the U.S. Open tennis tournament

Kim Kardashian arrives to watch a quarterfinal match between Serena Williams and Venus Williams at the U.S. Open tennis tournament

Kendall Jenner and Gigi Hadid react during pre-match festivities for a quarterfinal match between Serena Williams and Venus Williams

Kendall Jenner and model Gigi Hadi watch the quarterfinal match between Serena Williams and Venus Williams at the U.S. Open

Singer Joe Jonas, model Gigi Hadid andtelevision personality Kendall Jenner in the stands before the start of Venus Williams and Serena Williams quarterfinals match on the ninth day of the 2015 US Open Tennis Championship at the USTA National Tennis Center

Kendall Jenner  and Gigi Hadid watch as Venus Williams of the US plays Serena Williams during their quarterfinals match

Donald Trump attends the quarterfinals women's singles match between Serena Williams and Venus Williams at the USTA Billie Jean King National Tennis Center

Rapper Nas attends the Women's Singles Quarterfinals match between Serena Williams and Venus Williams

Tennis legend Billie Jean King (center) and USTA President Katrina Adams (right) attend the Women's Singles Quarterfinals match between Serena Williams and Venus Williams

A huge crowd of people wait outside the gates of Arthur Ashe for the night session with Venus and Serena Williams playing each other

Venus and Serena remain best of friends off the court, sharing a love for fashion and other interests while building separate lives.

'I feel like Venus and I have definitely proven that you can be friends and you can be sisters, you can be enemies on the court, and you can be friends and sisters off the court,' summed up Serena.

Serena first emerged unexpectedly, winning the U.S. Open singles title in 1999 at the age of 17, launching a magnificent career that has added 20 more slam singles crowns.

Featuring the biggest serve in women's tennis, Serena vaulted to dominance.

In 2003 she completed her first 'Serena Slam' by winning the grand slam season-opening Australian Open after she swept the last three titles of 2002 -- all against Venus in the finals -- to hold all four singles crowns at the same time.

There were lows as well in her majestic career, brought on by her temper and health issues.

In 2009 Serena lost a U.S. Open semi-final to Kim Clijsters after screaming a profanity-laced tirade at a female line judge who called a foot fault on her.

SERENA VS. VENUS: ALL THE FACTS OF THE WILLIAMS SISTERS 

BORN:

Serena Williams says she cant remember a time as a child when older sister Venus would not beat her at tennis

* Serena - In Michigan on September 26, 1981. (Age: 33)
* Venus - In California on June 17, 1980 (Age: 35)
GRAND SLAM CAREER:
* Serena - 21 wins: Australian Open (2003, 2005, 2007, 2009, 2010, 2015); French Open (2002, 2013, 2015); Wimbledon (2002, 2003, 2009, 2010, 2012, 2015); U.S. Open (1999, 2002, 2008, 2012, 2013, 2014)
* Venus - seven wins: Wimbledon (2000, 2001, 2005, 2007, 2008); U.S. Open (2000, 2001)
HEAD-TO-HEAD:
* Overall - Serena leads 15-11
* Quarter-finals or earlier - Venus leads 5-3
* In grand slams - Serena leads 8-5
* At U.S. Open - Tied 2-2
CAREER TITLES (INCLUDING GRAND SLAMS)
* Serena 69
* Venus 46
WORLD RANKING:
* Serena - 1
* Venus - 23
PERSONAL LIFE:
* Born to Richard Williams and Oracene Price, the family moved to Florida when Venus was 10 so the sisters could attend a tennis academy
* Serena turned professional in Sept. 1995
* Venus turned professional in Oct. 1994
* Serena won first WTA title in Paris in 1999
* Venus won first WTA title in 1997
* Serena is third on the list of female grand slam title winners
* Venus is equal 12th on the list
WORLD NO. 1 SERENA:
* Serena Is one of only five women, after Maureen Connolly, Margaret Court, Martina Navratilova and Steffi Graf, to hold all four grand slam titles at same time.
* She also owns 13 women's grand slam doubles titles with Venus and has won four Olympic gold medals: Singles (2012), doubles (2000, 2008, 2012).

World No. 1 Serena Williams considers sister Venus 'the best player in the tournament' 

* Beat Martina Hingis in the U.S. Open final in 1999, becoming the first African American woman to win a grand slam singles title since Althea Gibson in 1958.
* Failed to make another grand slam final until 2001 when she lost in the U.S. Open final to older sister Venus.
* Missed the 2002 Australian Open with injury then embarked on an incredible run that included winning five of the next six grand slams and losing in the semi-finals of the 2003 French open.
* Career affected by injury over the next four years, winning two Australian Open titles in 2005 and 2007 but failing to advance beyond the quarter-finals at the other three.
* Won U.S. Open in 2008 to break the grand slam drought, having not won a major title since the 2007 Australian open.
* At the 2009 U.S. Open, Williams was fined $175,000 and placed on a two-year probation for unsportsmanlike behaviour in her semi-final loss to Kim Clijsters.
* Joined Billie-Jean King on all-time grand slam list in sixth with 12th grand slam title at 2010 Australian Open.
* She missed the U.S. Open in 2010 because of medical complications after cutting her foot on glass while celebrating her win at Wimbledon.
* In 2011, she underwent surgery after a life-threatening blood clot was detected on her lung. She made the U.S. Open final but lost to Australia's Sam Stosur.
* Won Wimbledon title in 2012 and followed that up with Olympic gold medal on the same grass courts beating top seed Victoria Azarenka in semi-finals and third seed Maria Sharapova in final.
* Won fourth U.S. Open title in 2012, beating Azarenka in the final.
* Crashed out to teenage compatriot Sloane Stephens in Australian Open quarter-final in 2013 but rebounded to claim her second Roland Garros title, one of 10 titles she wins that year to reclaim world top ranking.
* Knocked out early in 2014 Australian Open, but claims seven titles, including her sixth U.S. Open, which is her third in succession, to join compatriots Chris Evert and Martina Navratilova on 18 grand slam wins.
* Defeats Maria Sharapova in the 2015 Australian Open final to claim her 19th grand slam title.
* Despite battling a bout of flu, she wins a third successive major title and 20th overall by overcoming Czech left-hander Lucie Safarova in the French Open final.
* Claims so-called 'Serena Slam' by winning sixth Wimbledon crown to hold all four majors for the second time in her career. 

Serena then threatened to shove a tennis ball down the official's throat.

Docked a point on match point, she handed victory to the Belgian and was fined $175,000.

Health issues also held her back.

Serena missed nearly a year due to a severe cut to her foot following her 2010 Wimbledon victory and a subsequent clot in her lung.

But Serena worked her way back, rededicating herself to the game.

After taking on Patrick Mouratoglou as her coach just before Wimbledon in 2012, she has gone on an extraordinary tear, dominating the game at the advanced tennis age of 33.

In the past three-plus years, Serena has won eight grand slams and is riding a magical 2015 season in which she has registered a 52-2 record, three wins away from a career-crowing calendar-year Grand Slam. 

Serena Williams of the US (left) shakes hands with her sister Venus Williams during their women's doubles match against Sara Errani and Roberta Vinci of Italy on the nineth day of the Australian Open tennis tournament in Melbourne on January 22, 2013