Luis Castillo Scheduled for MRI to Evaluate Hamstring Strain

Mariners right-hander Luis Castillo exited Sunday’s game due to a left hamstring strain and is set to undergo an MRI on Monday for further evaluation. Castillo mentioned to reporters (including Adam Jude of the Seattle Times) through an interpreter that he first felt some discomfort in the fourth inning when he had to move on the mound to avoid a throw that never came from catcher Mitch Garver during an Ivan Herrera stolen base attempt. Just two pitches after Herrera’s steal, Castillo winced on the mound following his follow-through and was forced to leave the game after being attended to by trainers.

“The discomfort is present. We will be getting some tests done tomorrow just to determine the extent of the injury, but hopefully it’s not too severe,” Castillo said.

With the Mariners currently in contention for the AL West crown or a wild card spot, losing Castillo would significantly impact their playoff aspirations. Seattle has struggled offensively, but their strong suit has been their elite pitching staff. The rotation has been reliable and productive, with four of their pitchers (Castillo, Logan Gilbert, George Kirby, and Bryce Miller) ranking among the top 21 starters in MLB in terms of innings pitched this season.

Bryan Woo has dealt with a couple of stints on the injured list, leading to Emerson Hancock filling in for him and making nine starts. Hancock, currently in Triple-A, is the most likely candidate to join the rotation if Castillo is placed on the IL, although he has struggled to consistently perform at the big league level. In his limited MLB career, Hancock has posted a 4.76 ERA in 45 1/3 innings and a 4.50 ERA in 12 innings this season, along with a low 13.8% strikeout rate.

While Hancock serves as a solid sixth starter, replacing Castillo won’t be an easy task. Although the three-time All-Star hasn’t been as dominant as he was in his Cy Young-vote finish season in 2023, Castillo still boasts a 3.64 ERA over 175 1/3 innings this year. His strikeout and walk rates remain above average, and despite a slight dip in velocity on his four-seam fastball, it continues to be one of the most effective pitches in baseball.