PEORIA, Ariz. -- The most anticipated pitch in Mariners camp made its long-awaited debut in game action on Thursday, when Bryce Miller unveiled the splitter that he publicly shared he’d been working on all winter. And for the affable righty from Texas, even in a competitive environment, it still came with some humor.

Miller was told by Mariners manager Scott Servais and pitching coach Pete Woodworth that he could only throw four splitters, beginning a season-long effort to limit the usage to protect his arm given the taxing nature of the pitch.

So when Miller returned for the second inning and realized he’d yet to throw the splitter, he unleashed one to the leadoff man, then four in a row to the third batter -- one above the allotted tally.

“I went split, split, split,” Miller said. “So that was my fourth. Then I looked over at skip and Woody. And they're, like, waving at me like, ‘No more.’ And so I was like, 'All right.' But I shook to another split. I threw another one, and then I gave him a heater. So I threw five.”

Miller wound up generating a few whiffs on the splitter and finished with three strikeouts on other pitches in two innings, over which he gave up two hits and a run in the Mariners’ 6-5 loss to the White Sox. He also sat in the mid-90s on his fastball and topped out at 97 mph with a strikeout of Andrew Vaughn.

The splitter won’t be Miller's primary secondary pitch, but it could be a legitimate weapon against lefties, who had a .917 OPS against him compared to a .549 OPS from righties. That in itself was the genesis for something new following an end-of-season dissection of his arsenal.

He also drew upon conversations with Logan Gilbert and George Kirby -- who each added splitters last year to great success -- but didn’t actually toy with it until this winter due to arm-care purposes.

“We texted a little bit throughout the [offseason],” Gilbert said. “I saw his grips and everything he was posting online, so it looked pretty good.”

“I'm trying to slowly add it in and not come out the gates throwing 30% split,” Miller said. “I've got to take care of the forearm and elbow. Plus, all the other stuff, I need to work on that, too. And the other stuff is good as well. So don't want to get splitter-happy too early.”

A review of Miller’s rookie year truly shows an all-encompassing arc, one that began with the righty almost exclusively blowing fastballs by some of MLB’s best hitters, saw him take midseason lumps once hitters adjusted to that strategy and concluded with a retooling of his pitch mix by season’s end.

By then, Miller had added a two-seam fastball and was more comfortable with his changeup. Even the changes to his breaking balls were hard to keep up with, given that he threw multiple variations of a slider.

“He probably made more improvement at the big league level than any young pitcher I've ever seen, between what he was like when he got there to where it was at the end of the year,” Servais said. “And that's hard to do, to make those kinds of adjustments in the big leagues when you're that young and that inexperienced, and he did it.”

Miller took the analysis of his development even further on Thursday, saying that he’s a “totally different” pitcher than in late September after consulting with new teammates Mitch Garver and Luke Raley, whom he faced in outings during that final month.

“By the end of the year, I was pretty fatigued,” Miller said. “I don't know, my arm really felt fine, but it was like the whole body was fatigued. I was at an area where I've never been. ... But then after, once I start throwing, there are 10 consecutive bullpens, I'm like, 'All right, this is boring, I'm ready to get back in a game.'”

Miller’s strong debut season -- and more so, his sky-high upside -- is why he was so coveted this offseason when the Mariners were aggressively in the trade market. Miller was at the top of the Twins’ wish list when the two teams were discussing a Jorge Polanco deal, and it was only after Minnesota came off Miller that a deal manifested.

New pitch, new outlook and new season for an arm who still has much in front of him.