Jon Rahm and Sergio Garcia booked quarter-final berths on Saturday at the WGC Match Play as South African's Erik van Rooyen and Dylan Frittelli were knocked out of the event.
Morning knockout matches set up afternoon last-eight showdowns to reach Sunday's semi-finals at Austin Country Club in Texas.
Third seed Rahm, the only top-16 seed to reach the weekend from group play, sank an 11-foot eagle putt to close out a 3&2 victory on the par-5 16th hole over South Africa's Van Rooyen after neither was more than 1-up through the first 13 holes.
"It was a tough match. We both kept hanging in there," Rahm said. "I knew I had to make (the eagle). I needed to rest the legs. I'm glad I made it."
Rahm's quarter-final foe will be US 30th seed Scottie Scheffler, who won 5&4 over English 60th seed Ian Poulter, the 2010 champion who rolled through the group stage unbeaten.
Scheffler never trailed, winning the third and eighth with birdies, matching all three birdies Poulter managed, taking the par-5 13th on a 13-foot birdie putt and parring the next to close out the Ryder Cup star.
"I got up early in the match and I just kept putting the pressure on him," Scheffler said. "A guy like that, you give him an inch and he'll flip the match on you, so I knew I couldn't give it to him."
Spanish 39th seed Garcia beat Canadian 48th seed Mackenzie Hughes 2&1 to book a quarter-final against French 31st seed Victor Perez, a 5&4 winner over Scottish 41st seed Robert MacIntyre.
Garcia birdied the ninth and 10th to seize the lead for good, won the 13th with an eagle and parred out from there to close out the victory.
"I hit some really good shots," Garcia said.
Perez won three of the first four holes with birdies and the first three holes on the back nine with birdies to advance in his event debut.
"I made a few putts early that got me into the match," Perez said. "Was able to make some great birdies to really give myself a big lead."
Garcia is pushing pal Perez for a spot on Europe's Ryder Cup team.
"We're actually pretty good friends," Garcia said. "Very much a high potential Ryder Cup player for this year."
Another likely Europe star on that squad to face the Americans in September in English 21st seed Tommy Fleetwood, who beat South African 64th seed Frittelli 4&3 thanks in part to an ace at the par-3 fourth.
Fleetwood won four of the first six holes, topped by the hole-in-one from 179 yards with a 7-iron.
"It was a smooth 7, carried onto the slope, and rolled back in," said Fleetwood, who delivered a matter-of-fact reaction to the ace.
"I did a good job sort of staying in the moment, staying calm, and trying to kick on from there," he said. "Make a hole-in-one, it's just one hole and then you've got to get on to the next one and keep playing."
Fleetwood closed out the win with a three-foot birdie putt to win the 15th.
"I just kept doing the right things and holed out really well," Fleetwood said. "Got off to the perfect start and just kind of kept it going."
His next foe is American 32nd seed Billy Horschel, who ousted US 53rd seed Kevin Streelman 3&1.
US 54th seed Brian Harman, four down after five holes, reeled off eight birdies in a row starting at the sixth and won seven consecutive holes before parring in to beat US 55th seed Bubba Watson 2&1.
"I was down. It was hard," Harman said. "Finally made a good putt on seven and from there it was off to the races."
The victory ensured Harman a spot in next week's world rankings top 50 and with it a berth in next month's Masters.
"I knew I had to win today," he said. "It feels pretty good."
Harman next plays 2013 Match Play winner and 2019 runner-up Matt Kuchar, the US 52nd seed who never led until the final putt in a 1-up victory over US 49th seed Jordan Spieth.
Results from Saturday's round-of-16 knockout matches at the WGC Match Play at Austin Country Club, Texas (x denotes seed):
Tommy Fleetwood (ENG x21) bt Dylan Frittelli (RSA x64) 4&3
Billy Horschel (USA x32) bt Kevin Streelman (USA x53) 3&1
Sergio Garcia (ESP x39) bt Mackenzie Hughes (CAN x48) 2&1
Victor Perez (FRA x31) bt Robert MacIntyre (SCO x41) 5&4
Scottie Scheffler (USA x30) bt Ian Poulter (ENG x60) 5&4
Jon Rahm (ESP x3) bt Erik van Rooyen (RSA x62) 3&2
Brian Harman (USA x54) bt Bubba Watson (USA x55) 2&1
Matt Kuchar (USA x52) bt Jordan Spieth (USA x49) 1 up
Tommy Fleetwood (ENG x21) v Billy Horschel (USA x32)
Victor Perez (FRA x31) v Sergio Garcia (ESP x39)
Scottie Scheffler (USA x30) v Jon Rahm (ESP x3)
Brian Harman (USA x54) v Matt Kuchar (USA x52)