The Cubs are adding another arm to their spring mix, signing right-hander Trent Thornton to a minor league deal with an invite to big league camp. The move, first revealed by his trainers at Tread Athletics, gives Chicago a veteran bullpen option who’s shown flashes of real value-especially during his time with the Mariners.

Thornton, now 32, has pitched parts of seven seasons in the majors, splitting time between Toronto and Seattle. His most recent work came with the Mariners, where he quietly put together a solid stretch: a 3.65 ERA across 140 2/3 innings from 2023 to 2025. That includes a 2024 campaign where he logged 72 1/3 innings with a 3.61 ERA, showing he could handle a steady workload out of the ’pen.

Last season, though, was a bumpier ride. Thornton posted a 4.68 ERA in 42 1/3 innings before a torn Achilles cut his year short.

That ERA was inflated by one particularly rough outing early in the year, but even so, the injury was a tough blow for a reliever who had just started to find his stride. The good news?

According to his trainers, he’s ahead of schedule in his rehab and already throwing off a mound. Sources say he’s expected to be full-go for spring training.

Thornton’s path to this point has been anything but linear. He debuted as a starter with the Blue Jays back in 2019, throwing 154 1/3 innings over 29 starts.

The following seasons saw him shift to the bullpen, where he struggled to find consistency in Toronto. But the move to Seattle proved to be a turning point.

In 2023, he pitched to a 2.08 ERA over 26 innings with improved command and a more refined pitch mix.

One of the keys to that improvement? A shift in approach.

Thornton leaned heavily on a mid-80s slider, throwing it more than half the time in 2024. He paired that with a fastball that averaged 95.5 mph, giving him a solid one-two punch.

Over his time with the Mariners, he struck out 22.5% of batters while walking just 6.6%. His ground-ball rate sat at 39.7%-a tick below league average-but his ability to limit damage and keep hitters off balance made him a valuable piece in Seattle’s bullpen.

Now, he’s hoping to carve out a similar role in Chicago.

The Cubs’ bullpen picture is already fairly crowded heading into spring. Offseason additions like Phil Maton, Hoby Milner, Hunter Harvey, and Jacob Webb bring depth and experience, while the club also re-signed Colin Rea and Caleb Thielbar.

Add in Daniel Palencia, and you’ve got a group that’s mostly set. But there’s always room for a surprise, especially in the bullpen-where injuries and performance swings are part of the game.

Thornton likely isn’t walking into camp with a guaranteed spot, but he’s got a chance to pitch his way into the conversation. Think Brad Keller last year-another non-roster invitee who turned a spring opportunity into a bullpen job and a solid payday. If Thornton shows he’s fully healthy and can recapture his Mariners form, he could be one of the first call-ups if the Cubs need reinforcements early in the season.

For now, it’s a low-risk, potentially high-reward move for Chicago-and another shot for a veteran reliever looking to prove he’s still got something left in the tank.