NAPA, Calif. — Jon Rahm is motivated, even if he’s not feeling well.

The top-ranked Spanish star had two birdies and two bogeys Thursday in an even-par 72 in the first round of the Fortinet Championship, leaving him well back of the leaders at Silverado Resort and Spa.

Chez Reavie had the lead at 65, with Cameron Tringale and Adam Hadwin a stroke back. Six others were two off the pace. Masters winner Hideki Matsuyama was at 69, and Phil Mickelson shot 70.

“I was having a hard time focusing given the fact that I haven’t had a solid meal since Tuesday morning,” Rahm said. “My best guess is just a little run down from the season. Maybe having a little bit too much good rich food Monday and Tuesday just did it for my stomach.”

Rahm began feeling ill earlier this week and pulled out of the pro-am Wednesday to rest. He said he felt worse than when he tested positive for COVID-19 in June and was forced to withdraw from the Memorial after leading by six strokes through three rounds.

“Way, way worse,” Rahm said. “That Saturday I couldn’t have given you any more diagnosis than maybe a light cold based on what I was feeling that day. I would have never guessed it was COVID. So yeah, I feel way worse right now than I did.”

After the disappointment at Memorial, he won the U.S. Open at Torrey Pines in June for his first major championship. He won the money title, the Vardon Trophy for the lowest scoring average and had 15 top-10 finishes.

Rahm, who is scheduled to play next week in the Ryder Cup at Whistling Straits, said he’s also motivated by being passed over in the player of the year honors that went to Patrick Cantlay. Cantlay who won the FedEx Cup after edging Rahm by one stroke at the Tour Championship.

“I played amazing golf,” Rahm said. “What could have been if certain unfortunate situations didn’t happen, right? I could have had maybe one more win and the chance to compete for a medal. To think it could have been better does nothing but motivate me. I know I can get better.”

Reavie worked his way to the top of the leaderboard after a bogey on his fifth hole. He picked up birdies on 16 and 17 to get back under par, then stormed through the front nine, closing with three consecutive birdies including an 18-foot putt that got the string started.

“It was kind of a slow start but I told myself to stay patient,” Reavie said. “I was able to hit some fairways on the back and give myself some good looks.”

Mickelson got off to a good start but fell back with two bogeys over a five-hole stretch on the back nine.

“I stopped hitting fairways,” said Mickelson, who has never finished higher than third at this event. “I’m making a few changes and my miss has gone from left to right, and it’s a little bit different to adjust to. I thought that it went pretty well with that in mind.”