Horschel advanced to the second round at Hazeltine National Golf Club, which, along with The Chaska Town Course, hosted the first two rounds of the stroke play portion of the tournament.
He will face David Merkow in the next round after Merkow toppled Ben Leong, 5 and 3.
Kevin Tway, the son of former PGA Champion Bob Tway and the 2005 U.S. Junior Amateur champion, knocked off Lloyd Saltman, 4 and 3.
'I played pretty well,' said Kevin Tway. 'I'm just trying to hit fairways and greens and putt pretty well. You have to make some birdies, so just capitalize on that.'
Tway now has a second-round match with Canadian Ryan Yip, who was a 2 and 1 winner over Jason Kang.
Oliver Fisher beat Drew Weaver, 2 and 1 on Wednesday and will meet Jim Renner, a 2 and 1 victor over Michael McGowan, Thursday morning. Jonathan Hodge scored one of the larger wins on Wednesday with a 6 and 5 thumping of Beck Troutman. That sets up a second-round duel with John Hahn, a 2 and 1 winner over Derek Fathauer.
Matthew Swan bested Canadian Greg Machtaler, 5 and 4 to advance against Ryan Posey, who needed 21 holes to stop Ben Fox.
Perhaps the most intriguing second-round match pits reigning U.S. Amateur Public Links champion, Casey Watabu, who defeated James Love, 1-up, and Trip Kuehne, who lost to Tiger Woods in the final of the 1994 U.S. Amateur Championship. Kuehne hammered Chris Rogers, 5 and 3.
Eddie Olson won 1-up over Michael Schachner and will meet John Kelly in round two. Kelly moved into round two with a 3 and 1 victory over Daryl Fathauer. Dustin Johnson, a 1-up winner over Justin Fraley on Wednesday, will tee it up on Thursday with Jon McLean, the most lopsided winner in the first round with a 7 and 5 thrashing of Jon Sauer.
Mark Harrell, who finished second in stroke play, did not fare as well in the match play. He lost 3 and 2 Roberto Castro, who will now face Joseph Bramlett, who knocked off Julien Guerrier, 2 and 1 on Wednesday.
Webb Simpson won his match 2-up against Todd Mitchell. That means he will meet Luke Bakke in the second round after Bakke beat Rory Hie 1-up after one extra hole.
Alex Prugh, a 2 and 1 winner against Daniel Summerhays, will battle it out on Thursday with Jeffrey Castle, a 3 and 2 victor over Tarik Can. Bronson La'Cassie outlasted Andres Echavarria 3 and 2 in the opening round and will play Mark Strickland, a 3 and 1 winner over Josh Esler.
Kyle Davis won 4 and 3 over Shane Prante and plays Jonathan Moore on Thursday after Moore dismantled Skip Berkmeyer, 6 and 5. Antti Ahokas bested Rhys Davies 4 and 2 to set up a match against Richie Ramsay, a 5 and 3 victor over Mark Leon, on Friday.
Rickie Fowler, who toppled Jeff Bell 5 and 4, will play Andrew DiBitetto on Friday. DiBitetto bettered Robby Ormand to the tune of 4 and 3. Pablo Martin took 21 holes to eliminate Tyrone Mordt and set up Thursday's battle with Greg Carlin, who sent Kevin Chappell packing after a 2 and 1 loss.
Both the second and third rounds will be played on Thursday with the quarterfinals on Friday and the semifinals on Saturday. The 36-hole final will take place on Sunday.