Rory McIlroy made a winning start at the WGC-Dell Technologies Match Play Championship but Matt Fitzpatrick's struggles continued with defeat in his opening group match in Austin, Texas.
Former champion McIlroy led from start to finish in his 3&1 victory over American Scott Stallings on Wednesday.
US Open champion Fitzpatrick, the top seed in group 11 at Austin Country Club, lost 5&3 against JJ Spaun.
Only the winners of the 16 four-man groups advance to the knockout stage.
World number three McIlroy was three up after six holes and Stallings, who rallied with birdies on the ninth, 13th and 16th, conceded after Northern Ireland's four-time major winner made a sixth birdie of the day on the 17th.
Spaun took control of his match with Fitzpatrick with birdies on the third and fifth but the Englishman responded with an eagle on the sixth to reduce the deficit.
However, Fitzpatrick, who has missed the cut in three of his last four starts, conceded on the 15th after Spaun had birdied the 11th and 12th before an eagle on the 13th and a final birdie for good measure.
Elsewhere, Tyrrell Hatton struggled with pain in his right hand and arm following a warm-up shot as he suffered a 3&1 defeat by Ben Griffin.
World number one Scottie Scheffler finished one up on Davis Riley but world number two Jon Rahm was beaten by Rickie Fowler, who finished two up against the Spaniard.