Red Sox left-handed pitching prospect Hayden Mullins said he tried to add a two-seam fastball to his pitch mix “for the longest time.”
“For some reason I cannot get it to move,” Mullins said, laughing. “So we just stick to the old four-seamer.”
The old four-seam fastball does the job as Mullins elevates it and pairs it with two different sliders to get a high swing-and-miss rate. He finished with the fourth highest strikeout percentage (30.3%) among Red Sox minor league pitchers who faced at least 300 batters in 2024. He punched out 118 of the 389 hitters he faced.
Mullins, who turned 24 in September, enjoyed a strong season in his first full year back from Tommy John surgery. He posted a 3.94 ERA and .223 batting average against in 22 outings (17 starts) for High-A Greenville.
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The Red Sox have put an emphasis on adding pitchers to the organization with more swing-and-miss stuff. Mullins not only has the ability to miss bats but he’s a lefty who can get out right-handed hitters.
“In today’s game, I think it’s really important, especially swing and miss inside the strike zone,” Mullins said. “That’s been our focus this past year is just throwing everything in the zone and working off of it — and not trying to create swing and miss but creating pitches that are good enough that will produce swing and miss when they are in the zone. Because if you’re throwing a slider that moves 20 inches or whatever but it’s two feet off the plate, more often than not guys are not going to swing at it.”
The Red Sox drafted the southpaw in the 12th round in 2022, after he underwent Tommy John surgery his final year at Auburn. Boston took a similar approach the year before by drafting Hunter Dobbins after he underwent the same surgery in his final year at Texas Tech.
Dobbins, who the Red Sox recently selected to their 40-man roster, enjoyed a breakout season in 2023, his second full season back from the procedure.
Mullins is a strong breakout prospect candidate in 2025 (his second full year back) after a promising season in ‘24.
“Most guys that I have talked to that have had surgery, they say that it takes 18 to 24 months of throwing and stuff to actually feel like they are truly back,” Mullins said. “So hopefully that’s the case with me. I’m excited to get into next season and see.”
Mullins’ SoxProspects.com scouting report notes, his “fastball/slider combination has premium bat-missing ability. Fastball especially is extremely difficult to hit when he elevates it. Has pitches to get both right- and left-handed hitters out and the type of fastball teams look for.”
His fastball mostly sat from 91-94 mph and topped out at 96 mph this past summer.
“It plays up in the zone,” Mullins said. “Really, I just try to throw it down the heart of the plate … But whenever I throw it up, guys seem to swing and miss.”
He mixes in two different sliders.
“We call one of them a cutter just to differentiate for the catcher,” Mullins said.
Mullins said the slider they refer to as a cutter plays as a true depth gyro slider. He spins it well.
“The other is a sweeper like they have most of us throwing,” Mullins said. “I started throwing it a little bit last offseason, trying to work on it and stuff knowing they were going to add it.”
He began using it against hitters during spring training.
“I feel really confident in the cutter/depth slider,” he said. “I think it plays a little bit better off of my fastball profile because it’s more depthy and it plays off that high fastball look and tunnels well with it. And the sweeper, I felt a lot more confident than I first did whenever I started throwing it.”
But he said he needs to throw that pitch with the same shape more consistently.
“This season I’d throw some that would sweep up to 17, 18 (inches) and then I’d throw others that only swept to 10, 11, 12 (inches),” he said. “So I think consistency is going to be a big key on that one.”
Mullins also throws a changeup, the pitch he’s focused on most this offseason.
“Really trying to lock that down because like I said with the sinker/two-seam thing, for some reason getting that stuff to move that way and getting that depth is really tough for me,” Mullins said. “But we’ve been focusing on the changeup pretty heavily recently. Switched the grip within the last two to three games or starts of the season. And it actually was playing a lot better towards the end of the season than it was at the start. So I was really happy to see that progress.”
Mullins threw a seam-shifted wake changeup for most of the season. That’s a pitch 2024 AL Cy Young winner Tarik Skubal has used to dominate hitters.
“We have a slow-motion camera in Greenville that you can zoom into the pitcher’s hand and see how it’s coming off and how the ball flight is,” he said. “So we looked at that and we said this seam-shifted one is not going to work because of how my hand’s working through the ball.”
So he and the coaches decided to change to a four-seam grip.
“And just throw it like a fastball,” he said, adding that he began to see more velocity and increased horizontal movement with the new grip.
“So that’s been the focus this offseason is finding the spot to where that’s consistent and I can throw it in the zone whenever I want,” he said.
He’s also focused on gaining weight this winter.
“I’m not the biggest guy,” said Mullins who is listed at 6 feet but added that he’s 6 feet “in spikes.”
He weighs approximately 185-190 pounds right now, down from 195 pounds during the 2024 season.
“The focus right now is just putting on as much muscle and body weight as I can, try to get anywhere around 200, 195, 205, in that range and hold it throughout the entire offseason because I tend to lose a little bit of weight throughout the season,” he said. “Anything I can do to keep that weight on throughout the season is going to be great.”
Mullins averaged 4.2 per nine innings, a number he thinks can drop next year.
“I would attribute a little bit of it to coming off surgery and stuff,” Mullins said. “The ball feels a little bit different in your hand and you’re just getting back to game situations and all that stuff. We’re working hard along with velocity, gaining weight and trying to throw everything heart of the plate and let it move whatever direction it moves. And I think that will come with just experience, handling the moment, pitching more often, more frequent.”
