Robson left surprised as Morita’s early submission ushers her into second round at Flushing Meadows

Morita called for the trainer after the first game of the second set and, after a brief assessment of what appeared to be a right shoulder injury, she decided she could no longer continue.

During the hour and one minute of play, 17-year-old qualifier Robson competed well with Morita, ranked 46th in the world, and had just broken the Japanese player’s serve for the fourth time when play was halted.

Robson was playing in the main draw of the event for the first time after coming through qualifying and certainly looked more relaxed than she had during her qualifying victories over Taylor Townsend and Ling Zhang.

British No 4 Robson had mixed feelings about the nature of the result and was taken by surprise when Morita called it a day.

“I didn’t realise she had a shoulder problem until she walked to the chair after the first set,”she said. “I noticed she was talking to her coach and there were some actions going on.

“Then I thought maybe there was something wrong but I definitely didn’t think she was going to retire but I’m obviously really happy to be through to the second round.”

In the biggest shock of the women’s first round draw, Petra Kvitova became the first reigning Wimbledon champion to lose in the first round of the US Open in the Open era when she went down 7-6 (7/3) 6-3 to Alexandra Dulgheru of Romania.

The Czech has had a difficult time since beating Maria Sharapova in the final at the All England Club in July, winning only two matches,

Andy Murray, meanwhile, is confident he has learned from his US Open disappointments of the past two years as he prepares to start his Flushing Meadows campaign today.

The world No 4 made his grand slam breakthrough in New York in 2008 when he reached the final but in 2009 he did not make it past the fourth round and last year he was knocked out in round three.

With the final grand slam of the year coming three-quarters of the way through a long season, Murray believes fitness and preparation are the key, and that is something he believes he has got right this time.