Gary Woodland is the second player to withdraw from the Match Play, conceding his match to Rory McIlroy.
Tournament officials say Woodland has withdrawn for personal reasons. A statement was expected later.
McIlroy had to win Thursday to avoid elimination, though that remains in play. If Soren Kjeldsen defeats Emiliano Grillo, the Dane wins his group because he was to play Woodland on the final day of round-robin play.
Woodland was the runner-up in Match Play two years ago.
Jason Day, the No. 3 seed, withdrew on Wednesday to be with his mother when she has lung cancer surgery.