Kollmann played at Cuesta College in 2014. He pitched in four games and threw 6 2/3 innings. He was hit by a pitch and scored a run in his only plate appearance. Kollmann went 9-0 with a 1.64 ERA and 56 strikeouts in 47 innings his senior season at Templeton High School when the Eagles were co-league champions. He is a wine and viticulture major.