Rafa Cabrera-Bello advanced into the WGC-Dell Match Play quarter-finals after Byeong-hun An withdrew from their round of 16 encounter at Austin Country Club.
The Spaniard was a surprise winner of Group 12 having entered the tournament as one of the lowest seeded players, while An needed a one hole play-off victory over Scott Piercy to advance from Group 5.
The 52nd seed was four up after 11 holes before fellow European Tour Member An, who made seven pars with a birdie and a bogey on the front nine, withdrew with a neck injury.
Cabrera-Bello, who has sealed his place at the Masters Tournament in two weeks' time with his performance in Texas, played brilliantly on Saturday morning, registering five birdies on the front nine.
"No one wants to win with the other guy withdrawing," said Cabrera-Bello. "I still feel like I played really good golf today and made lots of birdies. The only one mistake I made was on the second, I made bogey but the rest was really solid.
"I've been playing well all year. This week I've had good preparation. I came here early and got to know the course.
I'm happy with the way I'm playing and with the way I'm managing myself out there in match play - Rafa Cabrera-Bello
A tee-shot to inside two feet on the fourth moved Cabrera-Bello ahead and he put his third to similar range on the par five sixth to go two ahead.
An was doing very little wrong but could not keep up with Cabrera-Bello's early pace as the World Number 54 holed a 61-foot bunker shot on the eighth for another birdie.
An approach to six feet on the ninth then put Cabrera-Bello completely in control and both men would save par on the next two holes before An's withdrawal.
Cabrera-Bello will face Ryan Moore in the last eight after he beat fellow American and 63rd seed Patton Kizzire 4 and 3.