Gilbreath began his career with the rookie–level Grand Junction Rockies. In 2018, Gilbreath pitched for the Single-A Asheville Tourists, recording a 7-8 record and 5.04 ERA with 119 strikeouts in 116 innings pitched. He spent the 2019 season with the High-A Lancaster JetHawks, pitching to a 5-10 record and 5.81 ERA with 143 strikeouts in 28 appearances.[4]
On November 20, 2020, the Rockies added Gilbreath to their 40-man roster to protect him from the Rule 5 draft.[5] On April 17, 2021, Gilbreath was promoted to the major leagues for the first time,[6] however he was optioned down the next day without making an appearance. He was recalled to the active roster on May 1.[7] Gilbreath made his MLB debut that day and pitched an inning of relief, but allowed a home run to the Arizona Diamondbacks' Josh Rojas. Gilbreath was amongst the best Rockies relievers in his rookie campaign, posting an ERA of 3.38 in 47 games. He had 44 strikeouts in 42+2⁄3 innings. Gilbreath appeared in 47 contests for Colorado in 2022 as well. In 43 innings pitched, he posted a 2-0 record and 4.19 ERA with 49 strikeouts.
On March 7, 2023, it was announced that Gilbreath would undergo Tommy John surgery, ending his season before it began.[8]
On August 16, 2024, Gilbreath was activated from the injured list to make his return from surgery.[9]