Serena Williams of the U.S. (L) embraces her sister and compatriot Venus Williams after defeating her in their quarterfinals match at the U.S. Open Championships tennis tournament in New York, September 8, 2015. REUTERS

Reuters: Serena Williams kept her bid for a calendar-year Grand Slam intact by outslugging older sister Venus 6-2 1-6 6-3 in a power-packed quarter-final at the US Open on Tuesday.

Serena entered the match with a 15-11 head-to-head advantage over Venus but the high number of losses to her 35-year-old sibling represented the most posted by any opponent against the world number one, who knew she was in for a tough fight.

The 33-year-old top seed, winner of 21 grand slam singles titles, took charge of the opening set by securing service breaks in the fifth and seventh games of a match that felt like a heavyweight title bout after a brilliant start by Venus.

However, Venus looked more like the player who has claimed seven grand slam singles titles in the second set, unleashing her power and drawing groundstroke errors from Serena for two service breaks that sent the match to a third set.

Serena seized control early in the decider and rode the momentum to the finish in her quest to join Maureen Connolly (1953), Margaret Court (1970) and Steffi Graf (1988) as the only women to win Wimbledon and the Australian, French and US Opens in the same season.

Great moment

The sisters exchanged a warm hug at the end of the 98-minute battle and Serena was asked about their embrace in the middle of the massive Arthur Ashe Stadium court in an on-court interview.

“It’s a really great moment,” Serena said. “She’s the toughest player I ever played in my life and the best person I know.

“So it’s going against your best friend and at the same time going against the greatest competitor for me in women’s tennis, so it was really difficult today.”

Serena, who belted 12 aces and unleashed 14 winners off her blistering two-handed backhand, said once the match started, she forgot about sibling connections.

Television personality Kim Kardashian (C) watches as Serena Williams of the US plays against her sister and compatriot Venus Williams in their quarterfinals match at the US Open Championships tennis tournament in New York, 8 September - Reuters

“When I’m playing her, I don’t think of her as my sister, because she’s playing so well, hitting big serves and running a lot of balls down,” Serena said. “When you’re in the moment you don’t really think about it. We trained all our lives to be on this court...”

Before Serena was able to take control of the opening set, she had to contend with a barrage of huge serves and forehands from her big sister. The three-times defending US Open champion said it needed a mighty effort to hang on for the win.

“Holding serve in the third set was all I could do. She came out hitting so hard, just blasting every shot. I was on defence a lot,” she said of her 23rd-ranked sister.

“This is a big moment for both Venus and I,” she added. “We both have a chance to be in the semi-finals and it’s a grand slam so we both want to do the best that we can.”

Next up for Serena will be unseeded Italian Roberta Vinci, who earlier defeated France’s Kristina Mladenovic 6-3 5-7 6-4.

Djokovic repels net-charging Lopez to advance

Top seed Novak Djokovic was tested by net-charging Spaniard Feliciano Lopez in a duel of volleys and passing shots before booking a berth in the US Open semi-finals in the early hours of Wednesday morning.

On a hot, humid night at Flushing Meadows, Djokovic waged an entertaining battle with the 33-year-old serve-and-volleyer, before finishing off the 18th seed 7-2 in the fourth set tiebreaker to complete a 6-1 3-6 6-3 7-6(2) victory.

Lopez won 28-of-41 serve-and-volley points, while Djokovic countered with 33 forays to the net that produced 19 points for the world number one.

“He’s one of the rare players who actually serves and volleys after the first and second serves,” said Djokovic, winner of this year’s Australian Open and Wimbledon championships. “He’s got a very big serve.”

Lopez served up 14 aces, while Dojokovic registered nine.

“It was anybody’s game in the fourth set,” the Serb said. “I’m just glad to get through in four.”

Djokovic had beaten Lopez in their five previous meetings but the lefty was confident, coming off a Cincinnati hardcourt event where he reached the quarters with wins over Milos Raonic and Rafa Nadal before losing to world number two Roger Federer.

“My game plan was to be aggressive,” Lopez said. “He was having some trouble reading my serve.

“The match from my side was great. I have to be satisfied with the match I played with the number one player in the world. I couldn’t do any better today. He just was better in the tiebreaker in the fourth. I think I played a great match.”

Djokovic, 61-5 with six tournament titles this season, will face defending champion Marin Cilic of Croatia in the semi-finals. The ninth-seeded Cilic advanced with a five-set win over France’s Jo-Wilfried Tsonga.

Nine-times grand slam winner Djokovic reached his ninth successive US Open semi-finals and the 2011 champion expects another challenging match against Cilic, despite owning a 13-0 record against him.

“He hasn’t lost a match (here), 12 matches in a row, so I’m sure he feels confident,” Djokovic said. “I know him very well. I have played him many, many times. We are great friends.

“I know what to do and I’m hoping I can execute the game plan.”