Mariners to stick with a ‘piggyback' pitching plan, with a twist. Here's why.

Everyone involved has acknowledged that the situation isn't ideal, but at least Luis Castillo and Bryce Miller have a better understanding of expectations around their hybrid roles in the Mariners' piggyback pitching plan.

"Now, I think, we're all on the same page," Castillo said Friday afternoon, via team interpreter Freddy Llanos. "I feel better. All I can do is continue working and whatever situation they put me in, just do my best."

The implementation of the Mariners' piggyback pitching plan was always going to be a complicated and delicate process.

The plan became even more complex - and exploded into the preeminent talking point surrounding the team this week - when Castillo and Miller were left in the dark about important details.

The situation boiled over in the victory Monday over the Athletics when both pitchers made their frustrations known, overshadowing one of the club's best victories of the season.

That initiated meetings Tuesday during which manager Dan Wilson and pitching coach Pete Woodworth talked with both pitchers to try and clear the air. Club president Jerry Dipoto followed up one-on-one with Castillo and Miller to provide further clarity. Tensions were eased.

On Friday, the parties all met again at T-Mobile Park at the start of a six-game homestand, and general manager Justin Hollander followed up separately with Castillo and Miller.

Moving forward, Hollander promised them, the front office would be sure to over-communicate with them.

"I appreciate Jerry and Justin and everybody getting us on the same page and communicating," Miller said. "That was, I think, the main source of frustration for me and ‘Rock,' was just not really knowing what was going on and what the plan was. I had a few questions that I wanted to ask, and they answered them. And I'm good now."

A plan has been mapped out for the next three turns through the rotation, and here's how the Mariners will proceed with six healthy and productive starting pitchers.

The short-term plan

The piggyback will carry on for the series finale Sunday against the Arizona Diamondbacks. Miller will start and Castillo will follow out of the bullpen. Each pitcher will have roughly 75 pitches to work with.

For the next two turns, the club will go back to a six-man rotation.

The M's are at the beginning of a stretch of 16 games in 17 days, and giving all six starters one extra day of rest could be beneficial at this stage of the season.

In mid-June, after they concluded a 10-day, 10-game East Coast trip, the club's brass will reassess where things stand. It's possible the piggyback plan could return at that point, but no final decisions have been made.

It's worth reiterating: The piggyback experiment has worked its first two times. Castillo and Miller have combined to post a 2.12 ERA over 17 innings, with four runs on nine hits, five walks and 21 strikeouts.

Castillo has allowed two runs in 6 2/3 innings, an encouraging step forward after he began the year with a 6.34 ERA in his first nine starts.

Miller has been electric in his three outings since returning from the injured list on May 13, allowing four runs in his first 16 innings (2.25 ERA), with a 14-to-2 strikeout-to-walk ratio.

For the next three turns through the rotation, Miller will effectively have a normal starter's schedule.

"We're all very routine oriented," Miller said. "And it makes it a lot more difficult when we don't know how to prepare for the next couple days or the next week. So getting on the same page with that was big."

The long-term plan

Starting in mid-April, the Mariners' group of decision-makers met weekly to weigh pitching options upon Miller's return. Wilson and the pitching coaches, Woodworth and Trent Blank, were involved in the discussions, along with Dipoto, Hollander and assistant GM Joel Firman.

The club wants to keep both Castillo and Miller stretched out as starters, and neither pitcher wants to shift to a bullpen role full-time.

The consensus was that the piggyback was the best idea for now, though it isn't intended as a long-term solution.

Everyone played a part in the communication breakdown in properly relaying the details of the plan to Castillo and Miller.

The absence of catcher Cal Raleigh perhaps played a part, too. Wilson leans heavily on Raleigh to bridge communication between the manager's office and the clubhouse, and Raleigh - who has been in Arizona rehabbing an oblique injury - is generally known for his direct and honest communication.

Given the rash of injuries in this era of high-intensity pitching, the odds are not high that all six of the Mariners' starters remain healthy through the duration of the season.

If they are still healthy and productive two months from now, that could precipitate a change before the Aug. 3 trade deadline.

The ascension of top prospects Kade Anderson and Ryan Sloan could very well become a factor this summer, too.

Anderson, 21, has simply been the best pitcher in the minor leagues in his first season of pro ball, and Sloan, 20, is considered as talented as any pitcher in the entire Mariners organization.

It's certainly plausible that the Mariners could be intrigued enough come September to add both young arms to the big-league roster for a potential playoff push, which could further complicate an already delicate plan.

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This story was originally published May 29, 2026 at 11:39 PM.