Promising Red Sox Pitching Prospects: Hayden Mullins

It's been a while since the Red Sox were known for their pitching development successes. You could argue that the last dominant starter they drafted and developed was Jon Lester. That looks to have changed since Craig Breslow’s hiring and overhaul of the pitching infrastructure. Although the top of the rotation is still populated with trade and free agent acquisitions, many pitching prospects are showing their growth early on this season.

When Breslow was hired, one of his key points was overhauling the team’s pitching development, not just at the major league level, but also throughout the entire organization. His first act was hiring Andrew Bailey as the pitching coach to work on a new philosophy with the major league staff, but he didn’t stop there. Breslow continued to improve the infrastructure, hiring Driveline Baseball co-founder Kyle Boddy as an advisor and bringing in Justin Willard, who had formerly been the Minnesota Twins’ pitching coordinator, as director of pitching. The additions seem to be working out. Minor league pitching is improving, and pitchers are beginning to gain attention. On Thursday, we discussed Juan Valera. Friday was Brandon Clarke's turn. Today, we discuss Hayden Mullins.

Mullins is the oldest of the three players in this series. He’s currently 24 and pitching in Greenville to begin the season. A 12th-round pick in the 2022 draft, Mullins currently projects to be a reliever and could possibly move faster through the minor leagues if the organization transitioned him to that role. Mullins throws from a three-quarters arm slot with a high-effort delivery. He has a plus extension and a low release point. The left-hander mainly uses five pitches: a fastball, slider, curveball, changeup, and cutter.

Mullins' fastball is viewed as one of his better pitches, sitting 92-94 mph and reaching 95 mph with life. The pitch will jump on hitters when thrown up in the zone. It has one of the highest whiff of any fastball in the system. Command is still a work in progress, but it's a potentially above-average pitch.

Mullins' slider is another potentially above-average pitch, sitting sits 81-85 mph with tight, two-plane shape. He’s managed to showcase an advanced feel for it. He can land it in the zone when he wants or he can bury it down to induce chases. Mullins' curveball could be viable and is currently considered an average offering. The pitch sits 78-80 mph and has a bit more depth than the slider. However, after the curveball his other pitches begin to fall off. Both the changeup and cutter profile as fringe-average offerings. At its best, the changeup features deceptive arm action and late drop.

After pitching for Greenville in 2024, Mullins returned there to open the 2025 season and has impressed early on. While he's now old for the level, he's also off to a fast start. In those two appearances (one start), he’s thrown eight scoreless innings,while striking out 13 batters. He’s also been able to generate whiffs, getting a total of 26 whiffs across those eight innings.

In his season debut, Mullins went four innings, allowing four hits and a single walk while striking out six batters. He needed 76 and racked up 15 whiffs. His second appearance came on in relief, but also lasted four innings. It may have been even better, as Mullins allowed only two hits and struck out seven.

The real test will begin when Mullins is promoted to Double-A.

Interested in learning more about the Boston Red Sox's top prospects? Check out our comprehensive top prospects list that includes up-to-date stats, articles and videos about every prospect, scouting reports, and more!