Keller threw six shutout innings in his season debut for Double-A Altoona on Sunday. He struck out eight batters while allowing two hits and two walks.
The 22-year-old righty threw 49 of 77 pitches for strikes, mixing in plenty of changeups against a lineup stacked with left-handed batters. Keller is expected to spend the bulk of 2018 in Altoona, with a potential midseason promotion to Triple-A. There's a chance he could join the Pirates as a September call-up, but it's doubtful the organization promotes him to the majors any sooner.