Justin Dunn is a little behind Justus Sheffield but should get an extended look with the Mariners at some point in 2020. Like Sheffield, Dunn has a high-leverage reliever floor, but with no expectations to win in 2020, Dunn will get every chance to show he can stick in the rotation.
Dunn has a slightly higher upside than Sheffield, but a better chance to wind up in the bullpen, hence his ranking similar to Sheffield. Dunn is a good athlete with a 92-95 MPH that hits 96 when pitching in the rotation. As a closer at Boston College, Dunn would hit 98 MPH, but since becoming a pro, he has operated in the mid-90s.
Dunn backs up his fastball with an above-average slider that flashes plus. Dunn also has a changeup that is fringe-average at times but lacks the upside or probability of Sheffield’s, giving him a bigger chance to end up in the bullpen.
Dunn throws strikes but is more control than command, another thing he will need to straighten out to stick in the rotation. If the Mariners do decide to move Dunn to the pen, he can ditch the changeup, speed up his delivery, and pump up the heater to the upper-90s and ratchet up the slider another half grade or so.
Dunn could wind up as a #3 or #4 starter. Or he could end up as the Mariners closer in 2021 or 2022. Dunn is going to be valuable for Seattle in some capacity. Whether it be in the rotation, out of the bullpen, or as a trade chip, Dunn will be an important player in the rebuild.