LIV Golf’s Kevin Na withdrew from the Masters with an undisclosed illness Thursday following a poor start at Augusta National, while 2021 runner-up Will Zalatoris withdrew prior to teeing off because of a back injury. 

Na, who has finished in the top 15 in the last three Masters, completed the first nine holes, making a double bogey on the first hole before finishing his day 4-over 36.

Kevin Na during the first round of the Masters

Kevin Na of the United States talks with his caddie Kenneth Harms on the third green during the first round of the 2023 Masters Tournament at Augusta National Golf Club April 6, 2023, in Augusta, Ga.  (Patrick Smith/Getty Images)

Augusta National announced his withdrawal due to an undisclosed illness. 

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Mike Weir, the 2003 Masters winner who was in Na’s group, said he recalled Na expressing some discomfort earlier in the round. 

"Right there on 10 tee," Weir said, via ESPN. "But he said earlier he wasn't feeling well. So I'm not sure what's happening, but he told me earlier he wasn't feeling well."

Kevin Na at the Masters

Kevin Na of the United States reacts on the second green during the first round of the 2023 Masters Tournament at Augusta National Golf Club April 6, 2023, in Augusta, Ga.  (Christian Petersen/Getty Images)

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"I can't remember the last time played as a single," Weir added. "I'm sure at some point in my career I probably did, but I am struggling to find my memory bank where it was. So that was a strange back nine."

Na was one of 18 LIV Golf members competing in the 88-player field this week. 

Zalatoris also withdrew from the tournament before ever stepping on the course.

Will Zalatoris at the Masters practice round

Will Zalatoris of the United States walks up the 11th hole during a practice round prior to the 2023 Masters Tournament at Augusta National Golf Club April 5, 2023, in Augusta, Ga.  (Patrick Smith/Getty Images)

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He was the runner-up at the PGA Championship and U.S. Open last year and got his first PGA Tour win at the FedEx St. Jude Championship. The following week, at the BMW Championship, he suffered two herniated discs during a tee shot, ending his season.

The Associated Press contributed to this report.