Thursday was a day filled with upsets at the U.S. Junior Amateur. None was more shocking than Palmer Jackson’s victory over defending champion Michael Thorbjornsen.

Jackson held a 1-up lead over Thorbjornsen in their Round-of-32 match when he missed the green at Inverness Club’s par-4 18^th hole. But with Thorbjorsen facing a 5-footer for birdie to force extra holes, Jackson chipped in for birdie and the 1-up victory.

“I knew I had to make that chip because he had a 5-footer for birdie and he was making those all day,” Jackson said. “It feels really good to take him out.”

A few hours later, it was Jackson who was on the other end. The incoming Notre Dame freshman led Kelly Chin, 2 up, with four holes to play before Chinn birdied three of his final four holes to force extra holes. Chinn advanced to Friday’s quarterfinals with par on the par-4 first hole.

Match-play craziness defined the day. The Round of 32 included eliminations of co-medalists William Moll, William Mouw and Ricky Castillo. Castillo’s loss was especially shocking as the incoming Florida freshman was routed by Kento Yamawaki, 6 and 5.

That set the stage for the afternoon defeats of Alabama commit Canon Claycomb and top-ranked junior Akshay Bhatia, who was upended by Preston Summerhays, the son of instructor Boyd Summerhays and nephew of Tour pro Daniel Summerhays. Bhatia tied the match entering No. 18 before missing the green and failing to get up-and-down. Summerhays stuffed his approach and two-putted for par to advance.

With Bhatia out, the new favorite becomes England’s Joe Pagdin, who defeated red-hot Maxwell Moldovan, 4 and 3, in the Round of 16.

The quarterfinal matchups are as follows:

Deven Ramachandran vs. Bo Jin

Garrett Martin vs. Kelly Chinn

George Duangmanee vs. Joe Pagdin

Austin Greaser vs. Preston Summerhays