Born in Puerto Rico, Montalvo attended high school in Florida and became the Rangers' final pick (20th round) in the 2021 Draft. A former shortstop who stood out more for his athleticism than his pure stuff as an amateur, he has thrived as a full-time pitcher in pro ball. He transitioned from relieving in his 2022 pro debut to starting last year and logged a 2.83 ERA, .211 average-against and 107 strikeouts in 95 1/3 innings in Single-A. He was enjoying another solid season at High-A Hickory when the Rangers moved him to the Tigers in a Trade Deadline deal for Andrew Chafin.
Montalvo's four-seam fastball sits in the low 90s and tops out at 95 mph, playing better than its velocity because of its carry and arm-side run and the extension in his delivery, and he's also developing a sinking two-seamer. His best swing-and-miss pitch is a low-80s slider with good depth. He also has nice feel for a fading mid-80s changeup that shows flashes of becoming a solid offering.
An athletic mover who gets down the mound well, Montalvo combines quality extension with a low release height and flat approach angle, presenting an unusual look for hitters. He improved his control in the second half of last season, throwing more and better strikes. He profiles as a back-of-the-rotation starter and perhaps more if his stuff gets better as he adds more strength.