Guilbeau showed tantalizing raw stuff from the left side at the University of Alabama, but never fully got a handle on his control bouncing between the rotation and bullpen there. He signed after his senior year with the Nationals in the 10th round, continuing to pitch both as a starter and reliever in A-Ball early in his pro career. After fairly pedestrian results the first two years, Guilbeau transitioned full-time to the ‘pen in 2018 with immediate success. He pitched to a 2.52 ERA over 28 relief appearances, holding lefties to a paltry .184 average-against with no extra-base hits.
Eligible for the Rule 5 Draft after the season, Washington sent Guilbeau to the Fall League to get a longer look. He has pitched even better there, touching 95-to-96 mph with his fastball—up numerous ticks from where I saw the heater during the regular season. A hard slider in the 86-to-88 mph range is the go-to secondary pitch, and he’ll mix an occasional changeup with plus separation in the mid-80s. Guilbeau’s extra-wiry frame and slingy low three-quarters slot add serious deception, especially to same-side hitters. Limiting walks will still need to be a point of emphasis, as Guilbeau sprays the zone at times and falls into predictable fastball counts.
The Nationals have a tough call to make on Guilbeau, who is Rule V eligible despite turning 26 early next season and never pitching above A-Ball. His dominant line against lefties during the regular season (.184/.298/.184) and surprising velocity spike in the Fall League make him an attractive Rule V candidate, and one that could arguably stick on a big league roster facing same-side hitters. A late-blooming prospect that’s on the rise, Guilbeau looks ready to contribute in the big leagues sometime soon.