Mariners right-hander Luis Castillo exited Sunday’s game due to a left hamstring strain and will have an MRI on Monday to evaluate the extent of the injury. Castillo, speaking through an interpreter to reporters including Adam Jude of the Seattle Times, mentioned that he first felt discomfort in the fourth inning while attempting to move on the mound to avoid a throw from catcher Mitch Garver, which never came during Ivan Herrera’s stolen base attempt. Shortly after Herrera’s steal, Castillo winced in pain during his follow-through and left the game following a visit from the trainers.
“The discomfort is present. We’ll have some tests done tomorrow to determine the severity, but hopefully it’s not too serious,” Castillo said.
With the Mariners in contention for the AL West title or a wild card spot, losing Castillo would significantly impact their playoff chances. Despite Seattle’s struggles in several major offensive metrics, their elite pitching staff has been a major strength. The Mariners’ rotation, which includes Castillo, Logan Gilbert, George Kirby, and Bryce Miller, has been both effective and durable. Among the 21 MLB starters with at least 161 1/3 innings this season, these four Mariners stand out.
Bryan Woo has had two IL stints this season, and Emerson Hancock has stepped in for him, making nine starts. Hancock, who is currently at Triple-A, is the most likely option to fill in if Castillo is placed on the injured list. However, Hancock, a former top prospect, has struggled with consistency in the big leagues, holding a 4.76 ERA in 45 1/3 innings and a 4.50 ERA in 12 innings during his 2023 debut, along with a 13.8% strikeout rate.
Although Hancock is a solid sixth starter, replacing Castillo is no easy task. The three-time All-Star hasn’t been as dominant as he was in 2023 when he finished fifth in AL Cy Young voting, but he still sports a 3.64 ERA over 175 1/3 innings this season. His strikeout and walk rates remain above the league average, and while his four-seam fastball velocity has decreased from 96.3 mph in 2023 to 95.5 mph this year, it continues to be one of the most effective pitches in the game.