A 6’1, 215-pounder from Yorba Linda, Calif, Guillemette signed with USC after ranking as the No. 233 player and the No. 19 catcher in his recruiting class, according to Perfect Game. During two seasons with the Trojans, Guillemette was a multi-year starter who hit .299 with three home runs and 19 RBI as a freshman before batting .286 with five home runs and 27 RBI as a sophomore.
After transferring to Texas, Guillemette took over as the starting catcher, hitting .298 with 11 home runs and 60 RBI as his slugging percentage rose from .429 to .541. The 11 home runs hit by Guillemette ranked fourth on the team while his 60 RBI led the Longhorns. Guillemette was also finished second among Texas players with 18 doubles.