Red Sox to promote relief prospect Luis Guerrero to Triple-A Worcester

The Red Sox are promoting relief prospect Luis Guerrero from Double-A Portland to Triple-A Worcester, according to MiLB Central on X, the social media platform formerly known as Twitter.

Guerrero, 23, is currently regarded by SoxProspects.com as the No. 31 prospect in Boston’s farm system, which ranks ninth among pitchers in the organization. The hard-throwing right-hander was originally selected by the Red Sox in the 17th round of the 2021 amateur draft out of Chipola College (Marianna, Fla.) and signed with the club for $122,500.

In 43 appearances out of the bullpen for Portland this season, Guerrero has posted a 1.81 ERA and 3.37 FIP with 59 strikeouts to 30 walks over 49 2/3 innings of relief. He held opposing hitters to a .150 batting average against in the process of going 18-for-22 in save opportunities.

Among 131 Eastern League pitchers who came into play Tuesday with at least 40 innings under their belts to this point in the year, Guerrero ranks 33rd in strikeouts per nine innings (10.69), 32nd in strikeout rate (27.8 percent), third in batting average against, 16th in WHIP, first in swinging-strike rate (17.1 percent), second in ERA, and 19th in FIP, per FanGraphs.

While the strikeout numbers are undoubtedly impressive, Guerrero has had his issues when it comes to walks. Using the same parameters from above, he ranks 113rd in the Eastern League in walks per nine innings (5.44) and 117th in walk rate (14.2 percent). Dating back to the start of July, he has walked 12 of the last 87 batters he has faced.

A native of the Dominican Republic, Guerrero underwent surgery on his right knee as an infant and now walks with a limp as a result. He told The Boston Globe’s Alex Speier earlier this spring that he now has limited mobility in his knee since the muscles in that area did not grow like the others.

“[But] for pitching, you just need to bend [the back knee] a little bit,” Guerrero explained. “My knee bends just as much as I need it to.”

As a child, Guerrero moved from the Dominican to Boston and grew up near Franklin Park. He then moved to Miami for his senior year of high school and spent two years at Chipola before being drafted by the Red Sox in 2021. Guerrero did not make his professional debut until last June and made his way to High-A Greenville before the 2022 season came to a close. He was expected to return to Greenville for the start of the 2023 campaign as well, but showed increased fastball velocity and wound up breaking camp with Portland.

Since then, Guerrero has only seen his stock rise. Alongside Sea Dogs teammates Nick Yorke and Marcelo Mayer, the righty represented the Red Sox at July’s All-Star Futures Game in Seattle. Replacing left-hander Shane Drohan in suiting up for the American League at T-Mobile Park, Guerrero struck out the lone batter he faced — Rockies prospect Yanquiel Fernandez — on five pitches.

Listed at 6-feet and 215 pounds, Guerrero operates with a 96-98 mph fastball that tops out at 100 mph, an 81-85 mph splitter, and an 87-90 mph slider that features 10-to-4 break, per his SoxProspects.com scouting report. In order to reach his potential, he will need to work on refining his control and command of the strike zone moving forward.

With the minor-league season winding down and the WooSox fighting for a playoff spot, Guerrero is slated to join a Worcester bullpen that already features Nick Robertson, Justin Hagenman, Andrew Politi, and Ryan Fernandez, among others.