Mariners add bullpen depth in trade for RHP Trent Thornton, send INF Mason McCoy to Toronto

The Seattle Mariners have traded INF Mason McCoy to the Toronto Blue Jays for RHP Trent Thornton, per Jeff Passan of ESPN and Daniel Kramer of MLB.com, now confirmed by the club. In a corresponding move, the club announced they have moved LHP Marco Gonzales to the 60-day IL, leaving the 40-man roster at 40.

Recently designated for assignment by the Jays, the Mariners effectively jumped the line to snag Thornton by sending over McCoy. The 28-year-old infielder has spent the past two seasons in Triple-A Tacoma since being acquired via trade from the Baltimore Orioles for cash, delivering quality defense at the shortstop position and around the diamond. His offense numbers, including a 20-20 season in 2022 that he could possibly replicate this season, are both interesting and also undermined by the offense-happy environment of the Pacific Coast League. Both players will report to their new respective Triple-A clubs.

Thornton is a 29-year-old righty whose fly ball profile has not quite translated into consistent quality as a bullpen arm. Selected in the 5th round of the 2015 draft out of the University of North Carolina by the Houston Astros, Toronto acquired Thornton from Houston in the winter of 2018-19 for INF Aledmys Díaz. His debut came that following season, starting 29 games and throwing 154.1 innings with a 4.84/4.59/5.92 ERA/FIP/DRA for the Blue Jays as a 25-year-old, but he’s been primarily a reliever in the bigs subsequently.

The 6’0 righty has slightly toned down the leg kick displayed in the header photo above, but has a three-pitch mix leaning on a four-seamer sitting around 93-94, a sweeping slider in the low-80s, and a more vertical curve around the same speed. Here’s a look at that slider:

And the curveball:

Thornton’s slider has been a highly effective pitch, but its been thrown at a lesser frequency than his heater that hitters absolutely feast upon.

Initially my inclination is that the M’s hope to push Thornton to throw his slider more frequently, and perhaps more firmly. Thornton has typically had reasonable command, working in the zone with an average career walk rate of just 8.6%. Given that Thornton was designated for assignment and cost Seattle a depth infielder who has yet to debut at the big league level, I would not put too much stock into this acquisition, but the righty can really spin the ball, so Seattle may see something more to unlock.