Paris: The double calendar Grand Slam seemed to be a realistic prospect at the start of this weekend, but the collapse of Novak Djokovic’s 28-match winning sequence left - Serena Williams - who defeated Lucie Safarova on Saturday afternoon to claim her second major of the year - out on her own.

In Williams’s case, one can only marvel at a player who is capable of lifting the French Open title - traditionally the most physically demanding of the Slams - while suffering from a heavy viral infection.

Admittedly, there may have been those who scoffed at her rather theatrical displays in the last two rounds, especially in the semi-final against Timea Bascinszky. But as Williams did the media rounds after the final, she was clearly suffering. Her nose was streaming so much that her Ns and Ms sounded like Ds and Bs, while her occasional coughing fits made TV interviews hazardous.

Williams still finished both her last two matches as the stronger player, reeling off the last 10 games against Bacsinszky and the last six against Safarova. Even her garrulous coach, Patrick Mouratoglou, was rendered almost - but not quite - speechless after the semi-final.

“This is the difference between champions and every-one else,” he finally managed. “There is no logical explanation.”

Safarova, who defeated Maria Sharapova and Ana Ivanovic on her way to the Roland Garros final, has now lost all of her nine matches against Williams. The world No. 13 did win the women’s doubles final with the American Bethanie Mattek-Sands on Sunday, defeating Casey Dellacqua and Yaroslava Shvedova 3-6, 6-4, 6-2. The Czech said that she believed her opponent could win the calendar Grand Slam this year.

“She’s a great player,” Safarova said. “She has obviously got the experience. She won all those grand slams already. I think she can do it. If she’s at her best and is in great shape, she’s playing the best tennis.”

If Williams can play like this while virtually bedridden, and on a surface that is nowhere near as conducive to her massive serve as grass, how will anyone stop her at Wimbledon? The tournament is surely hers to lose, although the American emphasised that tennis can be an unpredictable game. “Some days when I’m healthy I don’t play as well,” Wiliams said. “Whereas sometimes when you’re not feeling well you’re forced to play better because you have no other options.”

That can be the only explanation of her bewildering Paris campaign.

- The Telegraph Group Limited, London 2015