Francesco Molinari edged ahead of Patton Kizzire at the turn as play got under way on the the opening day of the WGC-Dell Technologies Match Play.
The field of 64 had gathered at Austin Country Club for one of the highlights of the season and Italian Molinari was one up after nine holes in a nip-and-tuck Group 2 contest against Kizzire.
Justin Thomas was three up against fellow American Luke List at the turn, while in Group 15 Si Woo Kim and Gary Woodland led against Pat Perez and Webb Simpson respectively.
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.
In the other Group 2 match, top seed Thomas was firmly in control.
He 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 a 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.
European Tour Affiliate Member Perez was mounting a comeback against Kim in their match.
The South Korean won the first, second and fifth but Perez birdied the 12th and 13th to be just one down after 13 holes.
Woodland was two up against Simpson.
