(Updates after matches cancelled)
NEW YORK Aug 28 (Reuters) - Serena Williams's center court clash was among dozens of matches cancelled on Wednesday after rain washed out most of the day's play at the U.S. Open, forcing tournament organisers to drastically revise the schedule.
Officials were still clinging to hope that the showers would clear up long enough for Andy Murray to begin his title defence but 28 other matches were postponed because of the foul weather on the third day's play.
Only five matches were completed on Wednesday before the clouds opened, sending players and spectators scampering for cover.
Players made a brief return to the courts when the drizzle stopped midway through the afternoon but another downpour saw them retreat to the locker room, forcing organisers to start cancelling matches.
World number one Williams was due to play Galina Voskoboeva on the Arthur Ashe Stadium center court but their second round meeting was among the matches postponed to allow some of the men to play their first round matches.
The most notable case was Murray, who ended a 76-year British drought in the grand slams when he won the U.S. Open in dramatic fashion last year.
Because of the unique scheduling at the U.S. Open, where the men's first round is played over three days, the Scotsman was not scheduled to play his opening match until Wednesday night.
With over four hours lost during the day session and the forecast calling for another drenching in the evening, Murray might have to wait until Thursday before facing his first-round opponent Michael Llodra.
New York's fickle weather has been a major talking point at Flushing Meadows for years with each of the last five men's finals spilling into a third week because of rain delays.
The problem was exacerbated because of the controversial scheduling at the last grand slam of the year.
In addition to playing the men's first round over three days, the U.S. Open was the only grand slam where both singles semi-finals and finals were played on successive days, leaving no room for catch-up if rain falls on the last weekend.
Tournament organisers changed the rule this year, having a day off between the semis and final, but remain powerless to combat Mother Nature.
The U.S. Open is the only grand slam where the main stadium is not covered by a roof. For years, U.S. Tennis Association officials balked at the idea of building a roof because of the enormous cost of covering Arthur Ashe Stadium, the largest tennis stadium in the world.
But they have finally relented, announcing two weeks ago that they would commence a massive renovation program, which would include a roof, but not until 2016, at the earliest.
Each of the five matches that were completed on Wednesday before the showers arrived were decided in straight sets.
China's Li Na beat Sweden's Sofia Arvidsson 6-2 6-2 to ease into the third round while Poland's Agnieszka Radwanska, the third seed, defeated Maria-Teresa Torro-Flor of Spain 6-0 7-5.
Spain's Carla Suarez Navarro and Russia's Anastasia Pavlyuchenkova also won through to the third round while Marcos Baghdatis of Cyprus won his first-round match against Japan's Go Soeda 6-4 6-3 6-1.
"I was a little bit happy because at least I'm done for my job today," said Li.
"I was so lucky before the rain come that I was I finish the match so I don't have to wait and warming up and coming to the court again." (Editing by Frank Pingue)