This Red Sox Pitching Prospect Could Breakout Soon

[Cory Sparks]

 

Hayden Mullins could be the Red Sox next breakout prospect. This is someone who, in the midst of all of the prospect talent that Boston has, is kind of hiding in the grass in my opinion. In this video, we’ll break down what makes this guy so special, the role he’s playing and ultimately when we could expect to see him debut in the bigs. 

Background

For starters, Mullins really does have the chance to be a true diamond in the rough amongst the rest of the Red Sox farmhands. This is someone who was selected in the 12th round of the 2022 MLB Draft. He was one of the more highly touted arms out of high school in his 2019 class, but then he developed some elbow issues that hung around for three different seasons as a member of the Auburn Tigers. That hurt his draft stock, as he tossed just 53.1 innings across three separate campaigns before eventually having Tommy John surgery that year. 

The Red Sox had an appreciation for his intangibles, and he got to work in 2023, immediately projecting as a potential starter. 

2026 So Far

Three seasons later, the 25-year-old southpaw finds himself just a pair of steps away from the ultimate goal: becoming an MLB pitcher and toeing the rubber at Fenway Park. After logging over 84 innings of work with the Double-A Portland Sea Dogs in 2025, he returns to share his home venue with the Maine Monster and continues to look like a steady presence on the mound from that left side. In 2026, he holds a 3-1 record with a 3.58 earned run average. He’s got 49 strikeouts to 18 walks over the course of 32.2 innings pitched. Mullins has only relinquished 15 hits in that timespan. 

Strikeout Stuff

What is the team’s no. 14 prospect excelling at? Despite having elbow issues in the past, he’s come back as one of the more lethal punchout-oriented pitchers in Boston’s pipeline. Not only has he struck out 305 hitters through 229.2 innings pitched in his professional baseball career, but opposing hitters are batting a miniscule .187 against him. The southpaw leads with his 55-grade fastball, thanks to a plethora of carry on a primary offering that sits between 91-95 miles per hour. This pitch glides to his armside, and he supplements it with a low-80s slider, low-80s changeup and has a cutter that’s still in the developmental stages. Mullins should be even more dangerous the more he fledges out his arsenal. 

Walk Issues

While the left-handed pitching prospect has made a living off of deceiving hitters and missing bats, he’s also struggled to locate from time to time. This is someone who has quite the complex delivery, including a leg kick, ball-hiding twist and a relatively low release point. That allows him to be tough to time up, but all of this action can also prove to be counterproductive to his own goals of getting ahead in the count. Mullins, who has 116 career walks in just under 230 frames, could benefit from simplifying his delivery into something a little more repeatable.

Going Deeper Into Ballgames

Lastly, since this is someone who was recovering from Tommy John surgery, the Red Sox have made it a priority to be cautious with the current Sea Dogs’ starting pitcher. He ramped up from 89 innings in 2024 to a career-high 101.2 frames in 2025, and over his career, he’s averaging just north of four innings per appearance. If Mullins wants to be a member of a big league rotation one day, he’ll need to venture into the sixth inning more often.