Dietz repeated the South Atlantic League to begin 2018, pitching well enough to get promoted to High A Frederick. Despite starting the season strong, Dietz struggled badly upon moving to the Carolina League, where he completely lost his control and secondary pitches. Dietz posted an ugly 8.91 ERA across nine starts with Frederick, walking nearly 20-percent of batters he faced. He was moved to the bullpen late in the season.
It’s unclear whether the Orioles plan to keep Dietz a reliever, but he profiles best in the bullpen long-term. His fastball plays up in short stints, working in the 94-to-96 mph range and touching 97-to-98 mph often. He throws downhill with consistent heavy run, and there’s less pressure on his command and pitchability coming out of the ‘pen. Dietz struggled to spin his mid-80s slider late in 2018, but the pitch has flashed sharp action and depth in the past. He has always struggled with a changeup, though there’s less need for it in relief. If Dietz can put aside a disastrous second half of the season, the tools are still here for a solid setup reliever. Both his fastball and slider have above-average potential if he’s able to throw more strikes. Coming off the way he finished 2018, however, that’s a big if.