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 -- Baseball’s offseason has reached its final lull, but it’s also a period where players are beginning to ramp up physical activity, with some sharing their progress via social media. Yet aside from Ty France’s exploits at Driveline, there hasn’t been much public dissemination of what Mariners players are working on this winter.

The only real exception -- and it’s a seemingly big one -- is the splitter that Bryce Miller has regularly tinkered with throughout his offseason throwing program while training at Texas A&M, making him potentially the latest within the Mariners’ rotation to add the unique pitch to his arsenal.

Miller has teased video of the splitter via X throughout January while working out at his alma mater. The clips are quick cuts and without live hitters, but the reception has been positive.

“Bryce is someone who has really, really taken to the idea of pitch shaping, trying to get better, trying to find ways to take his whole repertoire of pitches to the next level,” Mariners general manager Justin Hollander recently said in a radio hit with Seattle Sports 710. “I'm excited to see what it looks like in the spring.”

The splitter was all the rave in camp last year, when Robbie Ray, George Kirby and Logan Gilbert were each toying with one. Gilbert, specifically, saw huge results with the pitch throughout 2023, as it became arguably his best weapon and created more deception within his repertoire. 

“Bryce and Logan are coming from a similar place,” Hollander said. “They come from high in that [arm] slot, working straight down. With the kind of ride and carry that his fastball has, which makes it really unique and kind of a unicorn in baseball. If he can get the feel for the split over time, it sets up to work nicely together, working vertically up and down in the strike zone.”

Gilbert, like Miller, leaned so heavily on his four-seam fastball during his rookie year, which at times was arguably the best on Seattle’s pitching staff, but also became predictable for hitters to decipher. Just after the 2023 season, Miller reflected on the intention to install a new pitch ahead of ‘24. Yet the splitter is a much more aggressive addition than the curveball and/or cutter that he initially suggested.

“The first month of the year, it was all fastballs when I was up here,” Miller said on the season’s final day. “And if you look at the last month, I think I was able to command five pitches. So just really going in being able to sharpen those up and improving in other areas that need to be improved. I'm excited to see where we end up.”

Indeed, Miller leaned almost exclusively on his fastball upon being called up on May 2, saying at the time: “Right now, it’s just kind of prove that they can hit it before I stray away from it.” Yet as the season progressed, that’s exactly what developed.

Miller added a two-seam fastball after a few starts as another weapon inside to righties, then leaned more on his changeup later in the season, complementing the slider and sweeper that he already threw. He also toyed with grips after suffering a blood blister on his middle finger that required an IL stint.

“I didn't realize how well the fastball would play,” Miller said. “And then as [hitters] began to adjust, I realized how much if I can improve on the offspeed -- because in the Minor Leagues, I'd just toss a couple of those in, they wouldn't ever have to adjust because it's like different lineups all the time. So if I can really sharpen up the offspeed -- and I'm really happy with where the fastball is. So just build off of that.”

“It's amazing the transformation that he has put himself through since the day we drafted him,” Hollander said.

At this time last year, Miller was on the cusp of the Majors, and his upside after a stellar rookie season drew calls from coveting trade suitors. And his acumen and ability to adjust make him a vital cog to the Mariners’ rotation, next year and well beyond.