Luis Castillo-Bryce Miller Piggyback Scenario Could Give Mariners a Needed Deadline Answer

The real value of the idea might be what it tells Seattle by late July.

May 24, 2023; Seattle, Washington, USA; Seattle Mariners starting pitcher Bryce Miller (50) and pitcher Luis Castillo (58) interact during the sixth inning against the Oakland Athletics at T-Mobile Park. Mandatory Credit: Steven Bisig-Imagn Images | Steven Bisig-Imagn Images

The Mariners’ rotation question is starting to feel less like a depth problem and more like a truth serum. That is usually what happens when too many arms have a claim to too few spots. But there’s still a difference between having depth and having clarity. Right now, the Mariners have plenty of the first one. The second one is where things get messy.

Adam Jude of The Seattle Times recently floated a piggyback scenario as one possible way Seattle could handle the squeeze, with Castillo and Miller potentially sharing a game instead of both being forced into a traditional rotation lane. That’s the kind of idea that makes you stop for a second.

Luis Castillo and Bryce Miller in a piggyback setup? One starts, one follows, and suddenly the Mariners are treating two established rotation arms like a tandem project.

At first, it sounds like a little much. Then you look at the situation again and realize it might actually be the cleanest messy answer available. The Mariners don’t need this to be a long-term solution. They just need it to buy them time.

Castillo has not opened the season like the rotation anchor Seattle expected. Through seven starts, he was sitting at 0-3 with a 6.29 ERA, 1.66 WHIP and 31 strikeouts over 34.1 innings, and the underlying contact quality has not exactly offered a comforting counterargument. He has a 12.4 barrel rate, 49.6 hard-hit rate and .374 xwOBA allowed entering this stretch, which is not the profile of a pitcher simply getting nickeled-and-dimed by bad luck.  

That doesn’t mean the Mariners should treat Castillo like some disposable fifth starter. But the current performance matters as well. 

Miller’s return only sharpens the issue. He threw five shutout innings on 61 pitches in his latest rehab start with High-A Everett and said he was ready to go, while Adam Jude reported that his next outing is likelier to come in the majors than in another rehab appearance. The Mariners have not boxed themselves into one public answer yet, with a return to the rotation, bullpen usage, a piggyback role, moving Castillo or Hancock to the bullpen, or even a six-man rotation all among the possibilities being considered.  

The piggyback concept sounds unusual. But that doesn’t automatically mean unserious. It could protect Miller from being asked to jump right back into full starter mode. And it could give Castillo a structured environment where the Mariners can see whether shorter bursts help his stuff play up. Despite his most recent rough outing against the White Sox, this could also avoid treating Hancock like the obvious casualty.

Luis Castillo-Bryce Miller Scenario Could Give Mariners the Deadline Test They Need

If the Mariners ran a Castillo-Miller piggyback plan, the goal should be to run it long enough to answer real questions. How does Miller’s stuff look after the rehab build-up? Can he hold velocity and command deeper into outings? Does Castillo look sharper if he’s not being asked to navigate a lineup three times? Does Hancock keep forcing the Mariners to respect his case?

Castillo’s résumé says he should stay in the rotation. Miller’s upside and recent track record say he belongs there, too. Hancock’s performance says he has earned a longer look. The bullpen, meanwhile, is always one bad week or one minor injury away from becoming a deadline priority.

That's why the piggyback idea is more than a novelty. It could become a runway to the trade deadline.

The Mariners can survive a strange arrangement for a while if it helps them avoid making a premature call. What they cannot do is let it become a way to avoid making a call altogether. By late July, Seattle should know enough.

Every contender goes shopping for relief help. Bullpen arms get expensive, and teams talk themselves into paying premium prices for two months of leverage innings. 

But what if the Mariners’ best bullpen addition is already in their own rotation crunch?

That doesn’t mean moving one of Castillo, Miller or Hancock to the bullpen would be painless. It would still be a real decision with real consequences. Still, one of those moves might eventually become the most efficient answer.

If the Mariners can turn rotation overflow into bullpen strength, they would be solving two problems at once. They would clear the rotation logjam while reducing the urgency to chase another reliever at the deadline. 

A Castillo-Miller piggyback plan could work because it buys the Mariners time. But the need for it says plenty about how uncomfortable their rotation picture has become. This is what happens when reputation, performance, health, workload and deadline strategy all crash into the same five-man structure.

The harder question is how long it can actually last. And the answer should be: until the deadline.

Whatever the answer is, the piggyback plan really should not be the destination. It should be the bridge. And if the Mariners use it correctly, it might give them exactly what they need before late July arrives.