“Hitting a forehand or a backhand is really challenging with tendon injuries, but we also always talk about touch in tennis, to hit a drop shot or something like that,” said Kessler, who did not know the specifics of Kvitova’s injury. “A tennis racket is the extension of someone’s arm, so not having the feedback from the fingertips to the same level of specificity that was there before can also be challenging.”

Kvitova had been scheduled to begin her 2017 season at the Hopman Cup in Perth, Australia, but pulled out earlier Tuesday with an existing stress fracture in her right foot. The Australian Open, the year’s first Grand Slam event, begins on Jan. 16.

Kvitova, 26, reached her career-high ranking of No. 2 in 2011, the year of her first Wimbledon title. Kvitova beat Maria Sharapova in straight sets in the final with a display of thunderous power from her swooping serve and percussive forehand. She was the first Czech to win a Grand Slam singles title since Jana Novotna won Wimbledon in 1998.

Kvitova routed Eugenie Bouchard for her second Wimbledon title in 2014.

After falling out of the top 10 this year, Kvitova surged in the second half of the year, winning a bronze medal at the Rio Olympics, WTA titles in the Chinese cities of Wuhan and Zhuhai, and a fifth Fed Cup title with her Czech teammates in November. She finished the year ranked 11th. Last week, she won the WTA’s sportsmanship award for the fifth time in six years.

Elite women’s tennis players have been violently attacked before, often with career-altering results. In 1993, top-ranked Monica Seles was stabbed during a match in Hamburg, Germany, and did not return to the sport for more than two years. When she did, her dominance subsided and she added only one Grand Slam singles title to her previous eight.

In 2007, sixth-ranked Anna Chakvetadze and her family were assaulted during a home invasion in Moscow. Chakvetadze, who had made the semifinals of the United States Open three months before, could not replicate that success, and she retired in 2013 at age 26.

Chakvetadze said Tuesday that she was “very upset” when she heard that Kvitova had been attacked, emphasizing that mental recovery from such an attack can be more difficult than the physical aspects.

“Especially when you got badly injured, you always ask yourself, ‘Why did it happen?’” Chakvetadze said. “Could I do something different in that situation? I got an arm nerve injury after they tied it up with TV cable, and it took one month to feel my arm again. With a knife, it’s even worse. I hope she will recover as soon as possible, mentally and physically, but it would not be easy.”