Defending AT&T Pebble Beach Pro-Am champion Daniel Berger was forced to pull out of the tournament because of a back injury, the PGA Tour announced on Wednesday.

Berger, the 16th-ranked player in the world, is the second big PGA Tour star to withdraw from the tournament. Will Zalatoris, runner-up at last week’s Farmers Insurance Open, withdrew on Tuesday after testing positive for COVID-19.

James Hahn also withdrew on Wednesday after testing positive for COVID-19.

Kevin Stadler will replace Berger in the Pebble Beach field.

Berger was a member of the winning U.S. team at the Ryder Cup at Whistling Straits in September. Last season, he made a 31-foot eagle putt at the 72nd hole to win the AT&T Pebble Beach Pro-Am by two strokes over Maverick McNealy, earning his fourth PGA Tour victory.

Berger has made just two starts this year, including a tie for 20th at the Farmers Insurance Open and a tie for fifth at the Sentry Tournament of Champions.