This story was excerpted from Daniel Kramer’s Mariners Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

SEATTLE -- Among an army of arms all possessing elite stuff, if there’s one pitch that the Mariners might need at its best down the stretch and, potentially into October, it’s the slider from right-hander Andres Muñoz. 

That might be a lofty declaration, but consider that Muñoz has been thrust more regularly into Seattle’s highest-leverage pockets since the club traded Paul Sewald. His four-seam fastball velocity has dipped from a 100.2 mph average in 2022 to 98.5 mph in August. At this time last year, the slider was arguably the best pitch in all of baseball. It’s shown some of those elite glimpses in 2023, but lately it’s been getting hit -- and hard. 

“It’s not that I feel bad with my slider,” Muñoz said. “I still have 100 percent confidence in throwing it, but sometimes you try to speed up a little bit and that is when your arm lags or things like that. But I keep working on it every day and I know there’s going to be one point when my slider is back 100 percent.”

Added manager Scott Servais, “I think it hasn't been the same, and I think he's aware of that. ... One thing, teams know it. Teams and guys are looking for it. You've seen him go out there and throw three or four straight fastballs and the guy is still looking for a slider.”

Muñoz isn’t throwing it in the low-90s like he was at the end of last year, but the velocity readings are mostly in line with the totality of 2022, from 88.6 mph to 88.2 mph, and its 48.1% whiff rate is also close to the 50.8% from a year ago. But the .229 batting average and .337 slugging percentage are up from the respective .126 and .176 marks he posted last year.

It’s been even more notable in August, when opposing hitters were 7-for-22 against the pitch entering the week, the most glaring knocks being the two doubles that led to a blown save and eventual loss last Wednesday in Chicago. Both were middle-middle, which may offer a more telling sign to what’s going on -- and that it may be a fixable issue.

Specifically, Muñoz’s slider is at its best when generating chases on the back foot to lefties and off the plate away to righties, or weak contact at the very bottom of the strike zone. 

“It had a little bit more depth to it than what we're seeing right now,” Servais said. “So it's a pitch that has been a little bit more inconsistent, and we need to get it back.”

Part of the challenge, Muñoz said, has been his tempo between pitches. Data isn’t publicly available on each player’s time to the plate, but team officials have said that Muñoz was the longest in 2022.

Seattle worked out most of those kinks with its pitchers over six weeks in Spring Training, but Muñoz was being eased into action due to offseason ankle/heel surgery, then he hit the injured list from April 9 until June 6 with a right deltoid strain, pushing him further behind from adjusting to the pitch timer.

In an admitted rush during an Aug. 13 loss to Baltimore, he was called for a balk that positioned the Orioles to score the game-winning run. The pitch was, coincidentally, a slider.

“That is the thing, you don't have to change your delivery because of the clock,” Muñoz said. “But sometimes you feel like you have to do it quicker.”

One positive has been that the two-seamer Muñoz unveiled in Spring Training has been effective at eliciting weak contact, with just an 80.9 mph average exit velocity against.

“I like it a lot, because especially in those situations when I don’t have my slider, I didn’t have [the two-seamer] last year,” Muñoz said. “Now I have another option to attack with.”

The ninth inning has been a hot topic since Seattle traded Sewald. Muñoz has contributed eight of the Mariners’ MLB-best 13 saves since but has also blown two in that stretch. Beyond the slider, the Mariners need Muñoz to be a late-innings linchpin -- precisely as he was when striking out the side to seal Sunday’s 3-2 victory, the last on a 90 mph slider for a backwards K. 

It was just one outing, but it looked much more like a moment from one of the AL’s best leverage relievers in 2022.