The Pirates continued their slow, methodical approach to Keller's development in 2018. Keller encountered little resistance at any point during his time with Double-A Altoona -- he allowed more than three runs just twice in 14 starts -- but nonetheless the team waited until the final day of June to bump him up to the next level. While the results took a turn for the worse after the leap to Triple-A, the peripherals were fine (24.2 K%, 0.52 HR/9). Keller's walk rates haven't been especially good at the higher levels, but he commands the fastball well. Fastball command is something a lot of young arms struggle with upon arrival to the big leagues, but that shouldn't be too much of a concern with Keller. He can keep the ball on the ground and the strikeout totals should be useful, if unexciting. Considering his path to this point, it seems likely that Keller will spend much of the first half back at Triple-A before finally cracking the big-league rotation.