Kreilach began his professional career with Rijeka in the Croatian first division, making his debut at 18 years old in the 2007–08 season, eventually playing 128 matches in six seasons while scoring 19 goals. He was the club's top goalscorer in the 2011–12 season with nine goals.
He then moved to Union Berlin in the German second division for five seasons, scoring 33 goals in 147 matches, highlighted by a 12-goal season in 32 matches in 2015–16.[3]
In February 2018, Kreilach signed with Real Salt Lake of Major League Soccer.[4][5] In his time at the club, he became the club's third highest-ever goalscorer with 47 goals, and acted as club captain during the 2022 and 2023 seasons. Kreilach left the club after six seasons in December 2023, joining fellow MLS side Vancouver Whitecaps FC[6][7]