Scouting Report

Video scouting report »

Scouting grades: Hit: 60 | Power: 50 | Run: 60 | Arm: 45 | Field: 55 | Overall: 55

A torn labrum as a sophomore and a knee injury as a junior dogged Gillen’s high-school career in Texas, but he showed enough as a healthy senior to get taken 18^th overall in the 2024 Draft. The injury bug carried over into pro ball with a calf issue delaying his debut in his first full season and a wrist injury from a slide into a base cutting him off early in mid-August in 2025. In between, he was one of Single-A’s most productive hitters with a .267/.433/.387 line with five homers and 36 steals across 73 games. His 151 wRC+ was tied for eighth-highest among 97 players aged 19 or younger with 300+ plate appearances.

From a slight hunched-over stance, Gillen dips a bit to gather energy and springs on balls with an affinity for extra-base hits to the pull side. He didn’t expand the zone during his first full season, leading to a 19.8 percent walk rate against Single-A arms. But that was needed because when he did chase, he often whiffed. He still gets to enough pitches and pitch types in the zone to be a potential plus hitter, and while his power wasn’t huge, he could still stand to add strength and in-game pop in his 20s.

With the knee issue behind him, Gillen’s plus speed translated quickly to the Minors, and he picked his stolen-base opportunities well, only getting caught three times in 39 attempts. The previous shoulder injury has dulled his arm strength, forcing a move from the infield as a prepster to center field as a pro. He made real strides defensively in terms of reading the ball off the bat, and his wheels cover up for other mistakes. Continuing his progression while healthy could enable Gillen to make a leap in his second pro season.

Video scouting report »

Scouting grades: Hit: 60 | Power: 50 | Run: 60 | Arm: 45 | Field: 50 | Overall: 55

Gillen underwent shoulder surgery to address a torn labrum as a Texas high-school sophomore, and a knee injury slowed him again as a junior. He was healthier as a senior in 2024, just in time to pop up Draft boards as the best prep prospect from the Lone Star State. The Rays selected Gillen 18th overall and signed him for full slot at $4,372,900 before sending him out for a brief assignment to Single-A Charleston to get his feet wet. 

The left-handed slugger impressed Tampa Bay evaluators with his bat-to-ball skills as an amateur. He uses a balanced stance in the box and quick hands to find the barrel, pushing liners around the diamond. He showed increased impact and raw power in his final year at school, and there’s the belief that even more pop is coming with professional strength training and instruction, which should enable it to get to above-average at peak. 

The injuries clouded Gillen’s outlook somewhat. He looked faster and faster the more he moved away from the knee issue, but scouts were worried that his arm was still below-average after the previous shoulder injury. The Rays were pleased enough with what they saw from the arm in pre-Draft workouts but did move Gillen from shortstop to center field immediately after signing him. It’ll be a transition out there, but the change should still allow the teenager to make the most of his athleticism. Tampa Bay officials praise Gillen’s makeup at every turn and believe he’ll take well to their player-development philosophies that continually turn out high-quality prospects. 

Scouting grades: Hit: 60 | Power: 55 | Run: 60 | Arm: 40 | Field: 50 | Overall: 50

Gillen emerged as one of the top talents in Texas' 2024 high school class three years ago, only to be slowed by a torn labrum that required shoulder surgery as a sophomore and a knee injury as a junior. Finally healthy again this spring outside of a minor groin ailment, he pushed his way ahead of the rest of the Lone Star State prepsters. He became the first first-rounder from Westlake HS (Austin) since Kelly Gruber went 10th overall in 1980 when the Rays selected him 18th overall. Tampa Bay signed Gillen for full slot at $4,372,900.

Gillen may have had the best bat of any high schooler in this Draft, and Tampa Bay evaluators certainly felt that way. He has a disciplined approach, quick hands and a sweet left-handed swing that combine to produce line drives to all fields. His hitting ability will allow him to get to most of his plus raw power, giving him a 20-homer floor, and he should develop more pop as he adds more strength to his physical 6-foot-2 frame.

Scouts get run times from solid to well-above-average on Gillen, who looks more dynamic than he did last summer now that his knee injury is further behind him. The former Texas recruit has better range to his left than his right at shortstop, but his arm hasn't bounced back from labrum surgery and will dictate a position change at the next level. The Rays have already said they plan to transition Gillen to the outfield in pro ball, hoping to get the most out of his speed on the grass.

Video scouting report »

Scouting grades: Hit: 60 | Power: 55 | Run: 60 | Arm: 40 | Field: 50 | Overall: 50

Gillen emerged as one of the top talents in Texas' 2024 high school class three years ago, only to be slowed by a torn labrum that required shoulder surgery as a sophomore and a knee injury as a junior. Finally healthy again this spring outside of a minor groin ailment, he has pushed his way ahead of the rest of the Lone Star State prepsters. He projects to become the first first-rounder from Westlake HS (Austin) since Kelly Gruber went 10th overall in 1980.

Gillen may have the best bat of any high schooler in this Draft. He has a disciplined approach, quick hands and a sweet left-handed swing that combine to produce line drives to all fields. His hitting ability will allow him to get to most of his plus raw power, giving him a 20-homer floor, and he should develop more pop as he adds more strength to his physical 6-foot-2 frame.

Scouts get run times from solid to well-above-average on Gillen, who looks more dynamic than he did last summer now that his knee injury is further behind him. The Texas recruit has better range to his left than his right at shortstop, but his arm hasn't bounced back from labrum surgery and will dictate a position change at the next level. He could become an offensive second baseman, his quickness makes center field a possibility and at worst he should produce enough offense to profile in left field.

Awards

Baseball America Low Class A All-Star

Year	Team
2025

CAR Post-Season All-Star

Year	Team
2025

CAR Player of the Week

Week	Team
05/25/2025

Transactions

Team	Date	Transaction
	03/01/2026	OF Theo Gillen assigned to Tampa Bay Rays.
	09/08/2025	Charleston RiverDogs activated OF Theo Gillen from the 7-day injured list.
	08/16/2025	Charleston RiverDogs placed OF Theo Gillen on the 7-day injured list.
	08/16/2025	Charleston RiverDogs placed OF Theo Gillen on the 7-day injured list.
	04/27/2025	Charleston RiverDogs activated OF Theo Gillen from the 7-day injured list.
	04/04/2025	Charleston RiverDogs placed OF Theo Gillen on the 7-day injured list.
	03/06/2025	activated OF Theo Gillen.
	08/27/2024	OF Theo Gillen assigned to Charleston RiverDogs from FCL Rays.
	08/27/2024	Charleston RiverDogs activated OF Theo Gillen.
	08/05/2024	OF Theo Gillen assigned to FCL Rays.
	07/26/2024	Tampa Bay Rays signed OF Theo Gillen.
	06/16/2024	College Workout activated SS Theo Gillen.
	06/13/2024	SS Theo Gillen assigned to College Workout.
	08/09/2023	SS Theo Gillen assigned to High School Workout.