Brixi had a 4-under 68 in the third round that was the best score of any competitor on Saturday. He birdied his final two holes to increase his lead on Sampson-yunhe Zheng, who shared the lead with Porter after two rounds.
The 16-year-old Brixi finished seventh at this event last year. The Czech Republic native, who resides in Potomac, Md., played an international schedule in 2018, highlighted by a win at the Kram Junior Open in Poland.
Graysen Huff and Jordan Batchelor are tied for third at 2 under. Both had rounds of 1-over 73 on Saturday.
Joe Lyons is solo fifth at 1 under.
Porter, meanwhile, is part of a five-man tie for sixth at even par, six shots off the pace. Porter, the recent Orlando International Amateur champion who plays for Florida State, had too many big numbers on the card Thursday, starting with a double bogey at the first. It resulted in a 77.
A year ago, Porter finished this event tied for first with Hayden Buckley but lost the title in a playoff.
