Mariners’ Gregory Santos Suffers Lat Strain, Won’t Be Ready For Opening Day

Mariners right-hander Gregory Santos sustained a “mild” lat strain while warming up yesterday and will not be ready for Opening Day, general manager Justin Hollander announced to reporters Tuesday (X link via Daniel Kramer of MLB.com). A precise timetable isn’t available, but Santos is expected to be down for a matter of weeks, rather than months.

The health of Santos and fellow setup man Matt Brash (or rather, the lack thereof) has been a major storyline for the Mariners during spring training. Brash at one point was feared to have sustained a season-ending injury, but he’s since been diagnosed with only elbow inflammation and cleared to resume throwing. Santos felt some discomfort near his teres major muscle early in camp and was briefly shut down. He resumed throwing a couple weeks back but felt a “pinch” during yesterday’s long toss session and reported it to the team, Hollander explained. That prompted an MRI, which revealed the current strain.

Uncertainty in the Seattle bullpen only grew when one of their depth options, righty Jackson Kowar, experienced elbow pain and was diagnosed with a UCL tear. He’ll undergo Tommy John surgery and miss the 2024 season as a result.

The Mariners, suddenly facing the prospect of three injuries in the bullpen, pivoted and signed free agent right-hander Ryne Stanek to a one-year deal late last week. He’ll give them another experienced arm to add to the late-inning mix, though Stanek is coming off something of a down season and won’t necessarily be able to replicate the level of performance expected from Brash and Santos.

The Mariners acquired Santos from the White Sox in a late offseason trade sending a Competitive Balance (Round B) draft pick and prospects Zach DeLoach and Prelander Berroa to the White Sox. It was a fairly steep price to pay, but Santos broke out with 66 1/3 innings of 3.39 ERA ball for the South Siders in 2023. He fanned a roughly average 22.8% of his opponents, turned in an outstanding 5.9% walk rate and kept the ball on the ground at a very strong 52.5% clip — all while averaging 98.8 mph on his sinker. Add in that he’s controllable for another five seasons, and the appeal becomes all the more clear.

Thankfully for the Mariners, it appears Santos has avoided the type of significant lat strain that has caused various pitchers monthslong absences in recent years. If he’s able to return early in the season, as today’s update suggests, then the Mariners figure to have one of the game’s better bullpens. Brash and Santos are high-end setup options for one of the game’s premier relievers: closer Andres Munoz. Stanek is a veteran option with setup experience who can work in the middle innings. Last year’s unheralded acquisitions of Gabe Speier, Tayler Saucedo and Trent Thornton all yielded excellent results, and even if that trio sees some regression, it’s a deep and talented group if the M’s can get their top names healthy at the same time.