Brooks Koepka, who was making a strong return in 2021 after several frustrating injuries, has withdrawn from this week’s Players Championship because of a right knee strain.

It is not the same knee that plagued him at the end of 2019 and into 2020. Koepka had a stem cell procedure on his left knee in late 2019 that kept him from competing in the Presidents Cup and saw him drop from No. 1 in the world to outside of the top 10.

“Brooks strained his right knee and he is scheduled to further consult with doctors this week to receive a more extensive evaluation and outlook,” said Blake Smith, Koepka’s agent, in a statement released by the PGA Tour. “We will be able to provide additional updates and information as we learn more.”

Koepka, who is ranked 12th in the world, had knee and hip issues for most of 2020 and missed the U.S. Open. He also did not qualify for the FedEx Cup playoffs. At times, the injuries were so frustrating that he wondered whether he could return to his major-winning form.

His victory last month at the Waste Management Phoenix Open was his first since the 2019 PGA Championship and the eighth of his PGA Tour career. He was not competing in this week’s Arnold Palmer Invitational but tied for second a week ago at the WGC-Workday Championship.

“There was a period of about two months where I questioned whether I was ever going to be the same, whether I was even going to be somewhat remotely the same golfer that I ever was,” Koepka said after his Waste Management victory.

“My knee, no matter how much work and pain I was doing with Derek Samuel, my trainer, it just felt like it wasn’t progressing. And that’s the frustrating part, when you feel like it’s not going anywhere. But we stuck with it. Those dark places, a lot of tears, questioning yourself, and in dark places mentally. You’ve got to come out of that. It takes a lot of effort just to get out of those places.”

The Players Championship begins Thursday.

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