Mariners Pitching Updates: Dipoto on Miller, Castillo, prospects

A lot of focus of the Seattle Mariners’ start to the 2023 season has been the offense, or lack of it. But the pitching has been arguably the best in baseball and was a big topic of conversation during Jerry Dipoto’s latest visit with Seattle Sports’ Brock and Salk.

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During the Thursday interview, the Mariners’ president of baseball operations shared some insight into a few MLB arms as well as the prospect side of things.

Bryce Miller has been “really impressive”

The Mariners’ top-rated pitching prospect entering this season was right-hander Bryce Miller, and he’s looked the part and then some since debuting on May 2.

In three starts, Miller has allowed just one earned run and eight total baserunners in 19 innings pitched.

In his first two starts, Miller leaned on his fastball against Oakland and Houston and  had no problems there. In his most recent start, Miller had to use the breaking ball more in Detroit.

“Really impressive. What you saw was frankly what he was doing in Arkansas in the early stages of the season in trying to prepare himself with a full arsenal to go out and do what he just did, which was adjust to a lineup that appeared to be on his fastball in the early going,” Dipoto said. “And that’s something that Bryce hasn’t or won’t run into very often, I suspect. But when you do run into a team that is on your fastball, you have to have an alternative measure, and he showed that he’s not a one-trick pony … I thought he threw some really good changeups, obviously leaned on his breaking ball quite a bit … I was very impressed.”

But Dipoto doesn’t think Miller will have too many issues with his fastball in his career.

“I don’t know that there’s too many guys you can point to with a better fastball and the higher spin rate than Bryce is creating right now,” he said. “It’s top two or three and on a given day, it might be as good as any in the business … It’s still a special fastball that separates itself from the pack.”

Long ball hurting Luis Castillo lately

After a hot start to the year, staff ace Luis Castillo has entered a bit of a cold stretch, having a 5.67 ERA over his last five starts. But Dipoto isn’t too worried about the All-Star righty.

“Still, I look at the body of work. Here we sit in the middle of May and he’s got a (3.31) ERA with 11 strikeouts per nine and 1.9 (walks per nine),” he said. “It’s pretty good over a nine-start body of work. But as it goes, these last few starts have been generally a slump for Luis.”

What has hurt Castillo of late, Dipoto said, is the “homer ball.” He’s allowed six home runs over his last four starts after not allowing a single long ball in his first five outings.

In a Tuesday loss in Boston, Castillo allowed three homers and seven runs (five earned) in five innings.

“‘The Rock’ is not easy to hit. And I think the Red Sox did a phenomenal job of barreling him up, forcing him into the middle of the plate and they didn’t miss when they got him there,” Dipoto said. “Luis typically doesn’t allow the ball to leave the ballpark. Over these last three starts, that’s what’s grabbed him. He’s built on getting the ball on the ground, striking them out and getting his groundouts … When you give up multiple-run homers, it tends to stain your ERA in a short sample. And I think that’s what you’re watching, and I don’t think that’s permanent. It’s a middle of the plate slump, and when he gets back to the edges, I think you’ll see the same guy we saw for the rest of his time with the Mariners.”

When Berroa, other Seattle Mariners prospects, could debut

A big strength of the Mariners’ farm system is on the pitching side of things with a few notable arms being in Double-A.

One arm that could soon debut is Prelander Berroa, a hard-throwing right-hander who recently moved to the bullpen.

“Pre has really taken to the bullpen. He’s throwing 98 to 100 with a wicked slider. It’s been a very seamless transition for him,” Dipoto said. “He had another excellent outing last night down in Wichita. He’s the type of guy that you could envision throwing into a major league situation and him just running with it. And that could happen at any point, really.”

A key thing the Mariners are looking at with Berroa, Dipoto said, is bouncing back outing to outing.

“Right now he is. You’d like to get him three outings in a week or back-to-back days to make sure he’s prepared for that,” he said.

The Mariners have had some success with moving former starters to the bullpen, most notablly Edwin Diaz back in 2016.

Dipoto said Diaz’s move to the ‘pen in the minors lasted about three weeks before he was called up.

“So it was very quick,” he said,

Could Berroa be on that kind of timeline?

“It’s not too dissimilar in the way we’ve laid it out,” Dipoto said. “We did plan the first 10 outings or so for Prelander in laying this out. But similar to what we did just a year ago with (Matt) Brash … Somewhere in between Edwin Diaz and Matt Brash therein probably lies the timeline for Prelander Berroa if this all goes well.”

Berroa isn’t the only pitching prospect making waves as Emerson Hancock and Bryan Woo have been throwing very well of late in Double-A.

“With Woo, who threw again last night, it’s hard to imagine getting off to a better start than Bryan Woo has gotten off to. Last night was another dominant outing for him in Double-A,” Dipoto said. “And Emerson is coming off of the best start of his minor league career (with his) highest strikeout total in his young career.

“The pitching that we thought was pooling up in Double-A has manifested. Miller’s already in the big leagues, the others are off to a terrific start. And they can pitch for any other team in the big leagues almost immediately. But right now,  when you have the kind of pitching we have, there’s probably not a direct route for them to be in Seattle anytime in the immediate future.”

Latest Andrés Muñoz update

The Seattle Mariners’ bullpen has been great to start the 2023 season, and that’s been especially impressive as star reliever Andrés Muñoz has been out for over a month with a deltoid strain.

Muñoz recently suffered another setback in his rehab, which required a PRP injection. Dipoto said that’s worked out very well, and that Muñoz is now in his throwing program and could go out on a rehab assignment in the near future.

“My understanding is that if is throwing goes well over the next two days, he’ll progress toward his mound work and then start building up his pitch count to get ready to go out on a rehab assignment,” he said. ” … We’ve taken very methodical steps to make sure that when Muni does get back here, he’s ready to do the things that Andrés does.”

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