Kevin Na recovered from a crushing defeat in his final Group 6 match to beat Matthew Fitzpatrick in a play-off and advance to the last 16 at the WGC - Dell Technologies Match Play at Austin Country Club.
Na had two wins from his first two matches and when he was four up after seven holes needing just a half against Chris Wood, his progress to the last 16 looked assured.
But Wood won seven of the next eight holes with the help of four birdies and an eagle to take the match 2 and 1, meaning the winner of the clash between Fitzpatrick and Justin Thomas would make a play-off.
Thomas was two up with five up to play but Fitzpatrick birdies on the 14th, 15th, 16th and 17th handed the Englishman a 2 and 1 win and an unexpected lifeline.
But Na regrouped and hit a stunning approach to the first to birdie in the play-off and will next face Bill Haas, who beat K.T. Kim with a birdie on the sixth play-off hole.
Lee Westwood beat Pat Perez in his final Group 3 match to get into a play-off against the American and Marc Leishman, which Leishman won at the second play-off hole with a birdie.
Leishman will face Phil Mickelson in the last 16, the left-hander maintaining his 100 per cent record in Group 14 with a 6 and 5 win over JB Holmes.
Na took advantage of a bogey-double-bogey start from Wood to quickly move two up and birdies on the fourth and sixth had the new European Tour Member in total control.
A bogey on the eighth saw him drop back and when Wood birdied the ninth, that triggered a brilliant run as he BMW PGA Championship winner went birdie-par-eagle-birdie-par-birdie.
A Na gain on the 16th offered some hope before the 17th was halved in pars.
Fitzpatrick had won the first against Thomas but the American hit back with wins on the sixth, ninth and tenth and remained two up with five to play before the three-time European Tour winner's big finish earned the play-off.
"Today I had it going and tell you what, Chris Wood just stepped it up," said Na. "He made four birdies and an eagle in a nine hole stretch. I made a couple of mistakes but I couldn't keep up.
It was frustrating I was in a play-off but I put that behind me. All I was trying to think about was being aggressive and it worked great - Kevin Na
"It was frustrating I was in a play-off but I put that behind me. All I was trying to think about was being aggressive and it worked great."
Danny Willett found his form to beat Russell Knox 4 and 2 in Group 11, meaning a win for Haas against Kim would force a play-off, with the American prevailing 4 and 2.
The duo parred the first five extra holes before Haas eventually broke the run.
Westwood knew only a win would do against Perez and he duly provided in a nip-and-tuck battle.
The players traded birdies on the fifth and sixth, and eighth and ninth with Perez the man to fight back each time, before Westwood birdies on the 12th and 13th provided some breathing room.
Westwood and Leishman both saw birdie putts on the first lip out 90 degrees in the play-off but the Australian would not be denied on the second.
In the other Group 14 match, Si Woo Kim beat Daniel Berger one up.
