Bryce Miller has a very, very good fastball. The problem for him as a rookie, especially after an incredible start, is that was pretty much all he had. Among pitchers who threw at least 2,000 pitches last season, Miller's 58.5% four-seam fastball usage rate was the fifth-highest in the league, and unlike guys like Justin Steele and Spencer Strider ahead of him, Miller didn't have a killer breaking ball to lean on for whiffs.
And he still might not. Miller threw his slider and sweeper 26 times between them in his debut against the Red Sox and garnered a swing on just two of them; in 2023, Miller's 10.4% swing-and-miss rate with those two pitches was in the 13th percentile for those combined pitch types. That's really poor, especially when he didn't have a killer changeup like Logan Webb to make up for it.
But he might now. Kirby debuted a new splitter to his arsenal in that first start and threw it 20 times, just behind the slider for his second-most used pitch. And it looked pretty dang good, garnering 10 swings and six whiffs, the most for any pitch type besides his fastball. It also allowed the lowest average exit velocity of any of his pitches. And, while he threw it in the strike zone just 25% of the time, he induced a chase on 40% of his out-of-zone splitters, a good way to garner both whiffs and weak contact. And, it could be a way to keep lefties from crushing him, something they did too often in 2023, when they hit .303/.358/.558 against him.
Miller still isn't perfect, of course. The Red Sox jumped on him for four earned runs, thanks to a couple of homers off his four-seam fastball that probably caught a bit too much of the middle part of the plate. Command remains an issue, as Nick Pollack noted here, as does Miller's tendency to drop his arm slot when releasing his breaking balls, an issue that I suspect is at the heart of his issues with those pitches – they grade out well from a movement and velocity standpoint, so it would make sense if he was diminishing those pitches' effectiveness by tipping them.
But, what might have changed for Miller is that he actually has an alternative option to turn to. Last season, he only really had the fastball, and when that wasn't working for him, he had nothing he could really pivot to. Now, he might.
