The Red Sox are promoting pitching prospect Hayden Mullins from High-A Greenville to Double-A Portland, as was first reported by Andrew Parker of Beyond the Monster.
Mullins, 24, has certainly gotten his season off to an encouraging start. In four outings (three starts) to open the 2025 campaign for Greenville, the left-hander posted a 1.06 ERA (2.22 FIP) with 27 strikeouts to three walks over 17 innings in which opposing hitters batted just .186 against him. He fanned six across four scoreless frames in his last time out against Hub City this past Thursday.
Entering play on Sunday, Mullins was one of 31 qualified pitchers in the South Atlantic League. Among those 31, he ranked first in strikeout rate (42.9 percent) and xFIP (2.10), second in strikeouts per nine innings (14.29), third in FIP and swinging-strike rate (16.5 percent), fifth in ERA, eighth in walks per nine innings (1.59) and walk rate (4.8 percent), 10th in WHIP (0.82), 13th in batting average against and line-drive rate (20 percent), and 15th in groundball rate (44 percent), per FanGraphs.
A former 12th-round draft selection of the Red Sox coming out of Auburn in 2022, Mullins received a $97,500 signing bonus but did not make his professional debut until August 2023 due to Tommy John surgery recovery and rehab. The Tennessee native spent all of 2024 with Greenville and has since compiled a 3.48 ERA (3.81 FIP) with 145 strikeouts to 45 walks over 106 total innings at the High-A level.
Listed at 6-foot and 194 pounds, Mullins throws from a three-quarters arm slot and incorporates a high leg kick into his delivery. As noted in his SoxProspects.com scouting report, the under-the-radar lefty operates with a four-pitch mix that consists of a 92-94 mph fastball that reaches 95 mph, an 81-85 mph slider, a 78-80 mph curveball, and an 81-83 mph changeup. He has flashed bat-missing ability with most, if not all, of his offerings.
Mullins, who turns 25 in September, is currently regarded by SoxProspects.com as the No. 29 prospect in Boston’s farm system, which ranks 14th among pitchers in the organization. He is not included in Baseball America’s or MLB Pipeline’s Top 30 Red Sox prospects list at the moment, but that could soon change if he shows that he can adjust and hold his own against more advanced competition in the upper-minors.
As he prepares to make the leap from High-A to Double-A for the first time, it is worth noting that Mullins can become eligible for this winter’s Rule 5 Draft if he is not added to Boston’s 40-man roster by the November protection deadline. The Red Sox will presumably use this promotion to help determine if Mullins is worthy of such a spot, though he could emerge as a possible trade candidate well before that decision needs to be made.
Regardless, Mullins is slated to join a talented pitching staff in Portland that– as of this writing– includes the likes of David Sandlin, Yordanny Monegro, Blake Wehunt, and fellow southpaw Connelly Early, among others. He will likely make his Double-A debut at some point during the Sea Dogs’ upcoming series on the road against the New Hampshire Fisher Cats this coming week.
