Patrick Mouratoglou said Serena Williams proved she can add to her incredible grand slam haul during the French Open and warned she will be "dangerous" at Wimbledon.

The American made it through to the fourth round at Roland Garros before a pectoral injury forced her to withdraw just before an eagerly-awaited showdown with old foe Maria Sharapova.

Williams is only expected to be out for a fortnight, so the 36-year-old is set to grace the famous grass at the All England Club.

Coach Mouratoglou was not surprised to see the 23-time major singles champion perform so encouragingly in her first grand slam since giving birth last September and thinks she can be a force at Wimbledon.  

Asked about her spirits after suffering an injury setback, he told Omnisport in Paris: "She was down, for sure, because she worked incredibly hard when she came to Mouratoglou Academy, the five weeks practice was incredibly intense.

"She's been working for a year, but those weeks just before Roland Garros was kind of a sprint where she gave everything.

"The start of the tournament was a bit rough, but she was starting to play better and better and she was starting the second week feeling confident, thinking she can win this one and suddenly because of an injury she is out, so it was very disappointing.

"If you take a step back you realise that she is playing great, she is competitive and that means she might be able to win more grand slams."

He added: "I was not surprised [with her French Open run] at all, because I said before the tournament she was ready. Physically she was ready, it was more about how good a competitor she would be but she is naturally a good competitor so it came back very fast. 

"She has two weeks off to help the muscle to recover, she should be fine for Wimbledon.

"For sure, with the way she plays she will be dangerous. How dangerous we will see, she's competitive. Serena competitive is not good for the others - but for me it is!"