Kolarevic played college football at Northern Iowa from 2018 to 2019. He was redshirted in 2017. He played in six games in 2018 before suffering an injury, recording 65 tackles (including 3.0 for loss), one interception, and four breakups. Kolarevic earned HERO Sports first-team FCS freshman All-American honors for his performance during the 2018 season. He appeared in 10 games in 2019, totaling 79 tackles (including 6.5 for loss), two sacks, one pass breakup, one forced fumble, and one interception that was returned for a touchdown. He was named the Missouri Valley Football Conference (MVFC) Defensive Player of the Week twice during the 2019 season, and also earned second-team All-MVFC honors. The 2020 season was cancelled due to the COVID-19 pandemic.
Kolarevic transferred to play at Nebraska from 2021 to 2022. He played in every game in 2021, accumulating 27 tackles (including 1.0 for loss). He again played in every game in 2022, recording 33 tackles (including 1.0 for loss) and one blocked punt. Kolarevic also had a game-sealing interception against Iowa on November 25, 2022.
After going undrafted in the 2023 NFL draft, Kolarevic attended rookie mini-camp on a tryout basis with both the Chicago Bears and New Orleans Saints in May 2023.
Kolarevic was signed to the practice roster of the Hamilton Tiger-Cats of the Canadian Football League (CFL) on August 1, 2023. He was promoted to the active roster on September 2, moved back to the practice roster on September 14, and promoted to the active roster again on October 25. He was placed on injured reserve on November 3, 2023. Overall, Kolarevic dressed in three games for the Tiger-Cats in 2023, recording one special teams tackle. He retired on May 6, 2024.
