SP Keider Montero
It has not been a great year for Tigers pitching prospects. Wilmer Flores and Ty Madden have both stagnated in Double-A. and Jackson Jobe missed the first half of the year with a back injury, though he has pitched very well since he returned. However, the last two prospects on this list are pitchers who have started to make a name for themselves, starting with Keider Montero.
Montero has some of the best stuff in the system. Some say the only pitcher in the system who has better stuff than him is Jobe. He has struck out roughly 12 batters per nine this season between High-A and Double-A. His surface numbers aren't amazing, with a 4.93 ERA in 85.1 IP, and he does have a rather high BB/9, but his FIP is 3.32 and his xFIP is 3.57, which suggests he is pitching better than his numbers would indicate. He's allowed a .373 BABIP as well, which suggests some bad luck.
He doesn't allow a ton of hard contact and gets a bunch of swings and misses. He can really spin it. His slider and curveball are both plus pitches.
Montero was recently promoted to Triple-A Toledo, where he will likely stay the rest of the year. He also seems like a good candidate for the Arizona Fall League in October.