Yarbrough spent the majority of 2015 with High-A Bakersfield in the California League, where he finished with a 4-7 record and 3.76 ERA in 16 starts. He posted a 4.11 strikeout-to-walk ratio, .266 batting average against, and 1.28 WHIP. Part of his high batting average against can likely be explained by his .324 BABIP, which was much higher than the .266 BABIP he finished with in 2014. Yarbrough had a groin injury in June that sent him to the 7-day DL, but should be healthy to start 2016. Yarbrough's arsenal of pitches includes an average fastball and curveball to go along with an excellent change-up. He moved up from number 11 to number eight on the Mariners prospect rankings during 2015 and is estimated to make the MLB during 2016. Scouts believe has back-of-the-rotation potential, but will most likely end up in the bullpen long-term. If Yarbrough pitches well to start 2016, there is a good chance he could be called-up to the MLB at some point as a lefty reliever.