Serena Williams feels short of matches and is considering taking a grass-court wildcard to improve her conditioning ahead of Wimbledon.

The former world number one's quest to match Margaret Court's all-time record of 24 major titles took a hit with a surprise 6-2 7-5 third-round defeat to Sofia Kenin at the French Open on Saturday.

The 37-year-old has been struggling with a left knee injury in recent months and had to withdraw from the Miami Open and Internazionali d'Italia, while a viral illness led to her retiring from a third-round match against Garbine Muguruza at Indian Wells.

Williams has played just 12 matches this year and is open to taking to grass before Wimbledon, where she last year made her first grand slam appearance after the birth of her daughter and lost to Angelique Kerber in the final, for the first time since Eastbourne in 2011.

"I'm definitely feeling short on matches, and just getting in the swing of things. I don't really like playing out points when I practice," said Williams.

"I have some time on my hands, so maybe I'll jump in and get a wildcard on one of these grass-court events and see what happens."

Asked how far away she feels from her optimum condition and whether she will be ready for Wimbledon, Williams said: "I'm pretty far away [from top shape], but the optimistic part is I haven't been able to be on the court as much as I would have. That's okay. At least I can start trying to put the time in now.

"I hope [I'll be peak condition for Wimbledon]. I'm still working on it and working on getting there. I think it will be enough time. We'll see, but I definitely hope so."

Kenin produced a string of fine groundstrokes to break twice in the first set and Williams suggested there was little she could have done in response.

"I think she played really well. I feel like she, in that first set in particular, she hit pretty much inches from the line, and I haven't played anyone like that in a long time," she said. "She actually played really well.

"I just think that the player I played today, she just played literally unbelievable. She really went out there today and did great."