Theo Gillen Breaks Through To Double-A and Is Hungry For More

It was only a matter of time before Tampa Bay Rays top prospect Theo Gillen was going to be promoted to Double-A Montgomery.

Gillen, Just Baseball’s No. 19 prospect in baseball, has seemingly exceeded all expectations at just 20 years old. He’s someone who has now found his way onto almost every Top 100 Prospects list across the industry with just 155 minor league games under his belt.

The 2025 season was a tumultuous one for Tampa Bay’s 2024 first-round selection, as he missed time with a calf injury and broken finger that limited him to just 73 games in his first full year in the minor leagues.

However, that’s given way to a banner 2026 season. Across his first 74 games across High-A and Double-A, Gillen is slashing .319/.423/.542 while showcasing a newfound power tool.

“Having the entire offseason to really work on my body, knowing what to expect going into the season, being ready to play as many games as you possibly can, was really helpful,” Gillen said.

The key, above anything, was a “healthy offseason,” as Gillen was able to focus on himself instead of constantly worrying about rehab and getting back to full health like we saw throughout the 2025 season.

His heightened focus is unlike anything else he’s experienced to this point, and it’s allowed him to evolve more as a hitter. He currently has 14 homers, 60 RBI, 14 doubles and four triples on the year. Each of those marks are career highs, and he’s played in roughly the same amount of games as he did all of last season.

Gillen has already blown his previous production out of the water, as evidenced by his 165 wRC+ with High-A Bowling Green before his promotion to Double-A. In his 27 games at High-A this year, Gillen hit north of .340 with an OPS over 1.000. These numbers were much improved after he hit .267 with an .820 OPS with Single-A Charleston the year prior.

“Figuring out my base, that was the biggest thing we went into the offseason focusing on,” Gillen said. “Being on time more, being early, being uncomfortably early were a few things we hit on. … Adding strength and keeping that strength on as the season goes on.”

It was a slower-than-expected start upon his promotion to Double-A, where he is batting .246 with a .725 OPS. Those numbers look concerning on the surface, but for a 20-year-old, he has room to grow. That’s exactly the reason why the Rays moved him up to the Biscuits when they did.

While it would have been nice to see him carry his success to the next level, his offense struggles out of the gate with Montgomery showcase an offensive profile that’s yet to be completed. That said, the month of July has benefited Gillen, as he has raised his average to nearly .300 with an OPS north of .882 this month.

There’s still work to be done, and Gillen is well aware of that.

“[Rays fans] should expect a competitor,” Gillen said. “I’m going to go out and compete. I’m going to try to win every pitch, try to beat the pitcher. … I try to keep things as simple as possible and just try to win. That’s all I’m about.”

Keeping it simple has benefitted himself greatly and is a great contributing factor to his meteoric rise on prospect lists across the industry.

He’s someone who was a top-70, top-80 or even a top-90 prospect in the game coming into the year and is now among the league’s brightest future stars on both sides of the ball.

“At the end of the day, it’s a kid’s game,” Gillen said. “We’re going to go out there, we’re going to be kids, we’re going to have fun.”

The hitting has spoken for itself, but Gillen has prided himself on his defense, which has gotten better over time, especially now that he’s been healthy all season long.

Playing a position the organization is looking to fill down the line, Rays fans are right to be high on the Westlake product because he has all the tools to be a cornerstone piece at the big-league level.

“You’re just trying to take it day by day, pitch by pitch, and have fun with it,” Gillen said. “I’m just going to go out and learn as much as possible, and I’m not going to put a cap on that. I just want to learn, I just want to grow as a human, as a baseball player and just see where that takes me.”