Theo Gillen is on a summer tear as his ascension as one of baseball’s elite prospects continues.
MLB's No. 9 prospect added another impressive performance to his ledger with his first Double-A homer as part of a multihit outing – his second at the level – in Montgomery's 5-1 victory over Knoxville at Riverwalk Stadium. Gillen reached base three times on the night.
The Rays' No. 1 prospect roped a solo shot to right field off Knoxville starter Luis Martinez-Gomez (CHC No. 21) to even the score in the fourth inning. Gillen added his second extra-base hit off the night in the eighth with a two-run double off left-hander Evan Taylor that gave Montgomery some breathing room.
COMPLETE RAYS PROSPECT COVERAGE
Gillen has slashed an uneven .213/.304/.328 since his promotion to the Biscuits on June 22, though not much can be gleaned from a small 15-game sample size. His breakout night at the plate certainly comes as no surprise, especially given his thunderous run to start the year at High-A Bowling Green where he clubbed 12 homers in 57 games and posted a 1.038 OPS.
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Tampa Bay’s 2024 first-rounder impressed in his first snapshot of professional ball with a .820 OPS in 73 games for Single-A Charleston in 2025. The Rays have moved him along relatively quickly. He made his Double-A debut last month after just 138 games. The 20-year-old is also among one of the fastest risers on MLB Pipeline's Top 100 Prospects list, ranked No. 76 on the preseason list to No. 9 overall now -- including making the biggest jump of any prospect this year when he went from No. 39 to No. 10 in our recent top 100 update.
His bat is productive over a reasonable sample size, supporting the belief in his development with Montgomery. Gillen is beginning to show he's making adjustments, hitting safely in six of his past seven games with nine RBIs in that span.
The 20-year-old out of Westlake High School (Texas) sports a pair of 60-grade tools -- hit and run -- at the top of the Rays’ system. Gillen had a solid performance during the All-Star Futures Game, collecting an RBI single off southpaw Kash Mayfield (SD No. 4) at Citizens Bank Park.