New York (AFP) - Former champions Andy Murray and Maria Sharapova reached the second round of the US Open, Murray overcoming painful muscle cramps as well as Robin Haase.
Eighth-seeded Murray, who won his first Grand Slam title at Flushing Meadows in 2012, defeated the 70th-ranked Dutchman 6-3, 7-6 (8/6), 1-6, 7-5, but said the painful cramp that struck without warning could have cost him the match.
"I could have easily lost that match," said Murray, who thought he'd have been in real trouble in a fifth set. "I was very close to losing the match."
Fifth-seeded Sharapova, who lifted the trophy in 2006, rallied with a vengeance from an early break against fellow Russian Maria Kirilenko.
Trailing 2-4, Sharapova won the next 10 games to take the match.
"It's always tough to start here in New York," said Sharapova, who was just happy to be back under the lights on the Arthur Ashe Stadium court after missing last year's edition with a season-ending shoulder injury.
"It was tough missing this court last year," said Sharapova, wearing urban-chic black to mark the occasion. "I didn't follow the tennis too much -- it was a little too sad."
Sharapova's match was the curtain-raiser to world number one Novak Djokovic's clash with Diego Schwartzman.
The 22-year-old Argentinian is playing in his second career Grand Slam -- and the first tour-level hardcourt tournament of his career.
Top-seeded Djokovic, meanwhile, is eager to add another Grand Slam title to the seventh major crown he captured at Wimbledon.
Recently married and soon to be a father for the first time, Djokovic is gunning for a fifth straight US Open finals appearance and a second title to add to the one he won in 2011.
Murray hasn't reached a final at any level since his emotional Wimbledon triumph last year.
He appeared to be in firm control before staggering through the third set in obvious pain, and twice rallied from a break down in the fourth to finally close it out after just over three hours.
The 27-year-old Scot said he arrived at Flushing Meadows fitter than he has been for any Grand Slam of the year.
But the match against Haase left him looking for answers to his physical problems.
"I don't know exactly why it happened today," said Murray, who trains in the steamy heat of Miami and didn't think the 30 C temperatures on Louis Armstrong Stadium were excessive. "At the time it happened I wasn't exhausted."
With two-time defending champion Serena Williams and five-time champion Roger Federer not playing until Tuesday, four former champions were the opening day's headliners.
Venus Williams, the winner in 2000 and 2001, also advanced, defeating Japanese veteran Kimiko Date Krumm 2-6, 6-3, 6-3.
Australian Open winner Stan Wawrinka, seeded third, moved smoothly into the second round with a 6-2, 7-6 (8/6), 7-6 (7/3) victory over Czech Jiri Vesely.
Milos Raonic, the big-serving Canadian who is among the young guns vying to end the Grand Slam hegemony of the game's Big Four -- Djokovic, Federer, Rafael Nadal and Murray -- pelted Japanese qualifier Taro Daniel with 20 aces in a 6-3, 6-2, 7-6 (7/1) victory.
- Normal nerves -
Women's second seed Simona Halep shook off first-round jitters to defeat unranked US wildcard Danielle Collins 6-7 (2/7), 6-1, 6-2.
Agnieszka Radwanska showed no sign of big-tournament nerves, but the fourth-seeded Pole said she felt them nonetheless in a 6-1, 6-0 drubbing of Canadian Sharon Fichman.
"First match is always tricky," said Radwanska, who allowed her 112th-ranked opponent just three points in the second set.
Romania's Halep, who has quietly risen to number two in the world thanks to eight career WTA titles and with a little help from the injury-enforced absence of Li Na, admitted she was a bit intimidated to find herself first up for the tournament on the Ashe court.
"It's not easy to manage the situation, but I think after first set did I very well," said the 22-year-old who was runner up to Sharapova at Roland Garros. "I started a little bit nervous, but it's normal."