Bumpy Stretch For Rotation Blocking Mariners’ Breakthrough
One of the clear strengths of the Seattle Mariners at the beginning of the 2026 season was their starting rotation. Last season, they ranked fourth in Major League Baseball in innings pitched as a starting rotation and 11th in FIP (which is ERA but factoring out fielding luck).
Bryan Woo and Luis Castillo eclipsed 180 innings pitched. Two of their starters had an ERA better than 3.50. Three of them exceeded 160 strikeouts. Four of their starters made at least 23 starts last season. Eight different players needed to make at least two starts. For context, the World Series champion Dodgers had 14 different players make multiple starts. The American League champion Blue Jays needed 11 such starters.
They had one of the strongest, most reliable rotations in baseball last year. With the same cast of characters coming into 2026, the consensus was the Mariners would be able to lean on their starting pitchers to another postseason run. However, over the last few weeks, the starting pitching has not been the strength, but the weakness of this Mariners club.
Over the last 14 days, the Mariners’ starting rotation ranks 26th in ERA and 28th in WAR. Every single starter has had a clunker or two during those two weeks.
During that same stretch, the bats have come to life. They rank ninth in wRC+ and 13th in OPS during the last two weeks. Unfortunately, it has not synced up with good starting pitching.
The Mariners got back to .500 last week thanks to a 5-1 road trip. Right when they seemed to get momentum, they get swept at home by the Kansas City Royals, whom have a losing record. The first loss came with an uncharacteristically bad start from Bryan Woo, as he allowed six runs while striking out just two.
Emerson Hancock is free from all blame and guilt, as he had one of the best starting pitching performances in modern Mariners history, striking out 14 with zero walks in seven innings on Saturday. Unfortunately, lately, that is the outlier. Luis Castillo continued his season-long struggles on Sunday, allowing four runs, with his season ERA now sitting at 6.29. The question marks are getting bigger and louder for Castillo, who owns a 5.11 ERA in his last 17 starts, dating back to August of last year.
Even in the win Monday night against the Braves, Logan Gilbert allowed four home runs for the first time in his big league career.
Outside of Hancock, the rotation is in a bit of a funk. As a group, over the last two weeks, they rank 27th in barrels allowed. Teams are hitting the ball harder than normal against the Mariners’ starters. Perhaps this is just an ebb in the “ebb and flow” of a long baseball season.
The good news is, this rotation is too talented for this to last forever. With the bats finally waking up, once the rotation gets back in sync, this team can start rolling.
Seattle has reinforcements coming. Bryce Miller is currently on a rehab assignment. Last week, he made an appearance for Triple-A Tacoma, and his fastball touched 98.8 mph. Over his last two rehab outings, he has pitched seven shutout innings with 10 strikeouts.
The question is: who gets bumped out of the rotation once Miller returns, perhaps in the next couple weeks?
One idea is a six-man rotation. Another is moving someone to the bullpen, as the Mariners are currently suffering through an injury epidemic in their bullpen. Matt Brash, Gabe Speier, and Carlos Vargas are all on the shelf.
However it works out, if the Mariners are going to get on a roll, it needs to start with their starting rotation.
