4 Red Sox NRIs to watch this spring

The Red Sox struck gold with their non-roster Spring Training invitees in 2025.

The group featured 10 eventual Major League contributors, including three 2025 preseason Top 100 prospects in Roman Anthony (No. 2), Kristian Campbell (No. 7) and Marcelo Mayer (No. 12). Boston’s “Big Three,” as they were dubbed at the time, debuted last season and are in line for bigger roles in 2026. Additionally, utilityman Nate Eaton and lefty reliever Jovani Morán were both NRIs in 2025 and are on Boston’s 40-man roster entering the 2026 season.

This year’s crop of Red Sox NRIs may lack Top 100 prospects, but it does feature some intriguing names to watch. Here’s a breakdown of four NRIs to follow this spring.

Mikey Romero, 3B

There's one question swirling around Red Sox Nation right now: What will the infield look like come Opening Day? Willson Contreras is firmly locked in at first base and Trevor Story has shortstop taken care of, but Boston has two positions still in flux. Mayer, Campbell, Romy Gonzalez, David Hamilton and newly signed veteran Isiah Kiner-Falefa are candidates to shore up the dirt, but what about Romero?

Recently named as MLB Pipeline's No. 5 third base prospect in the game, Romero was one of the standouts in Boston’s system in 2025. The California native reached Triple-A at just 21 years old -- an impressive feat considering he dealt with injuries during his first two full pro seasons -- and led all Red Sox Minor Leaguers with 54 extra-base hits.

Romero has added 20 pounds since turning pro, leading to plus raw power and a career-high 17 homers in 2025. Originally a shortstop, the 2022 first-rounder has lost some speed as he’s matured but is still a capable fielder. This spring will give Romero the chance to face off against big league competition and allow Boston to determine how much more seasoning he needs at Triple-A.

Allan Castro, OF

The Red Sox left Castro unprotected from the Rule 5 Draft this winter, but he went unselected and remained with the organization. A switch-hitting outfielder, the 2019 international signee possesses average tools across the board but doesn’t have any abilities that jump off the page. After selling out for more pop and swatting a career-high 15 homers in 2024, Castro’s production last season resembled his 2023 campaign -- less power, but a better batting average. Across 92 contests for Double-A Portland, the 22-year-old slashed .268/.353/.753 with seven homers and 15 stolen bases. Castro doesn’t offer a super high ceiling, but he has a solid floor as a do-it-all reserve outfielder.

Noah Song, RHP

A 28-year-old isn't often still considered a prospect, but Noah Song is a rare example in which that’s exactly the case. Drafted in the fourth round in 2019 out of Navy, Song thrived in his seven-game professional debut in the now-defunct New York-Penn League before serving mandatory time in the military until February 2023. Prior to his return, Song was plucked from the Red Sox by the Phillies in the 2022 Rule 5 Draft. Upon joining his new organization, Song was placed on the injured list with a lower back strain.

Song pitched in rehab assignments across three levels in Philadelphia’s system before being returned to Boston after failing to make the Major League roster. That same year, he suffered an elbow injury that required Tommy John surgery and sidelined him for the entire 2024 season.

So what kind of pitcher is Noah Song now?

The 6-foot-4 right-hander, who ranked as high as Boston’s No. 6 prospect in 2020, moved through all five Minor League levels in 2025. He spent most of the season at Double-A, where he posted a 4.19 ERA with 44 strikeouts in 23 relief appearances. Once viewed as a surefire starter, Song’s future now likely lies in the bullpen. He still uses the same four-pitch mix that he did in 2019 (four-seamer, slider, changeup and curveball), with his four-seamer reaching 96 mph. Considering 2025 marked Song’s first full season on the mound since his college days, he could make a big leap this season and even join Boston’s bullpen.

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Jeremy Wu-Yelland, LHP

The Red Sox Minor League system was full of success stories in 2025, especially on the pitching side. But with Payton Tolle and Connelly Early hogging the headlines, Wu-Yelland flew under the radar. The 26-year-old, who has dealt with injuries since he was drafted out of Hawaii in 2020, transitioned to the bullpen in 2024 and made a significant jump last year. Over 25 appearances between High-A and Double-A, Wu-Yelland held opponents to a .201 average-against and racked up 71 punchouts. His 3.15 ERA and 1.07 WHIP were both career bests.

Wu-Yelland was a popular name this December during the Rule 5 Draft but went unselected. With Boston having just one proven left-handed reliever on its 40-man roster in Aroldis Chapman, Wu-Yelland has a realistic path to the Major League bullpen this season.