PARIS — It has been a frustrating year at the office so far for Serena Williams, filled with old injuries that have resurfaced and new ones that have scuttled her chances. It has been a season where the opportunities to play actual tennis matches and finish the few she has started have been far too rare.

But Williams was back in the public eye and in harm’s way at the French Open at age 37 on Monday, even if many other veteran tennis champions would have skipped the experience altogether and started preparing for the grass-court season and Wimbledon, which she has won seven times.

“It crossed my mind every day,” she said, when asked whether she had considered it. “But I’m here. And to do the best that I can do.”

In the opening set against the unseeded Vitalia Diatchenko on Monday, Williams’s best bore no resemblance to her finest tennis. She missed groundstrokes by the bunch and service returns by the bushel. She looked edgy and rusty.