Francesco Molinari made a winning start to his WGC - Dell Technologies Match Play campaign with a 3 and 1 victory over Patton Kizzire at Austin Country Club.
The Italian already has one World Golf Championships title to his name at the 2010 HSBC Champions and he put in a consistent performance to take a first step towards a second.
He shares top spot in Group 2 with Justin Thomas, who beat Luke List two up in a dramatic encounter.
The players in Group 15 could not be separated on day one, with Pat Perez and Webb Simpson both producing excellent fightbacks to halve their matches against Si Woo Kim and Gary Woodland.
Molinari moved one up early as he holed a 17-footer on the second for birdie but a nasty lie in a bunker off the tee at the par three fourth led to a bogey and Kizzire evened things up.
The American then hit the shot of the day so far as he spun his approach back into the hole at the fifth for an eagle and a one up lead but Molinari hit straight back with a birdie on the par five next.
The next two holes were halved in pars but a Molinari birdie on the ninth edged him back ahead at the turn.
He won the 13th with a par but dropped the next after a bogey before a birdie on the 16th and par on the 17th handed him a comfortable victory.
"It was a good match," said Molinari. "We both played well. I'm really happy with the way I played.
"It started well and then I missed a couple of chances to go up. Patton made two on five and we kept exchanging birdies. It was a good match until the end and I'm glad I came out on top."
Thomas won the first after List flew his second way over the green and while List won the second with a birdie, Thomas birdied the fifth, won the sixth with par and hit a stunning tee-shot into the seventh to move three up.
The World Number Two then produced his own contender for shot of the day on the ninth when he found himself on a steep bank covered in deep rough close to a wall but managed to get up and down for par and keep his lead.
List had bent his putter in frustration by this point but that did not seem to hinder him as he won the 13th, 14th and 15th with birdies putting with a wedge, although a bogey had seen him drop the 14th. The 17th was halved in pars before Thomas birdied the last.
European Tour Affiliate Member Perez had been three down after 11 holes but he birdied the 12th, 13th, 16th and 17th to take half a point.
Simpson had found himself three down at the turn but he fought back, winning the tenth, 13th, 14th and 17th on the back nine.
