Red Sox re-sign LHP prospect Eduardo Rivera to minor league contract

The Red Sox have re-signed left-hander Eduardo Rivera to a minor league contract, according to Alex Speier of The Boston Globe.

Rivera was slated to reach free agency next month, but is now tentatively in line to return to the organization he has spent the better part of the last two seasons with. The 22-year-old is currently regarded by SoxProspects.com as Boston’s No. 43 prospect, which ranks 25th among pitchers in the system.

Originally selected by the Athletics in the 11th round of the 2021 draft out of Colegio Cadest in Puerto Rico, Rivera joined the Red Sox as a minor league free agent shortly after being released by the A’s last May. The San Juan native split the remainder of the 2024 season between the Florida Complex League and Low-A Salem, then returned home to dominate for the Cangrejeros de Santurce and Indios de Mayaguez of the Puerto Rican Winter League.

After pitching for Puerto Rico in the Caribbean Series in February, Rivera understandably did not see much action in his first spring training with the Red Sox before breaking camp with High-A Greenville. Though he did not make his season debut until April 16, Rivera impressed to the tune of a 1.61 ERA (2.21 FIP) with 68 strikeouts to 16 walks in 10 outings (six starts) spanning 44 2/3 innings for the Drive. Opposing hitters in the South Atlantic League batted just .138 against him.

Alongside fellow lefty Payton Tolle, Rivera was promoted to Double-A Portland in late June. While Tolle was in the process of being fast-tracked to the major leagues, Rivera experienced some growing pains with the Sea Dogs. In 10 appearances (nine starts) for Boston’s Eastern League affiliate, he posted a 3.40 ERA (4.28 FIP) with 40 strikeouts to 30 walks over 42 1/3 innings in which opponents batted .214 against him. He ended the season on a high note by fanning seven and walking only one across six scoreless, one-hit frames against Binghamton on September 9.

Overall, Rivera finished the 2025 campaign having forged a 2.48 ERA (3.22 FIP) with 108 strikeouts to 46 walks in 20 appearances (15 starts) totaling 87 innings between Greenville and Portland. Among the 14 Red Sox minor leaguers who threw at least 85 innings this year, regardless of level, Rivera ranked first in groundball rate (54.5 percent), second in batting average against (.177), ERA, and swinging-strike rate (15 percent), third in strikeouts per nine innings (11.17), fourth in FIP and strikeout rate (29.7 percent), fifth in xFIP (3.33), and seventh in WHIP (1.16), per FanGraphs.

Listed at a physically imposing 6-foot-7 and 237 pounds, Rivera throws from a three-quarters arm slot and incorporates a very high leg kick into his delivery. As noted in his SoxProspects.com scouting report, the burly southpaw primarily operates with a five-pitch mix that consists of a 93-97 mph fastball that can reach 98 mph, an 87-89 mph cutter, an 83-86 mph slider, an 85-89 mph changeup, and a 78-80 mph curveball.

Even though Rivera is back with the Red Sox on a minor league contract, his status for next season is still technically up in the air since he is Rule 5-eligible this winter. In other words, Rivera could be taken by another club in December’s Rule 5 Draft if he is not added to Boston’s 40-man roster by the November protection deadline.

Given his past struggles with command and control, however, Rivera could very well be left unprotected by the Red Sox and then go unselected in the Rule 5 Draft. If that does turn out to be the case and he remains in the organization through the offseason, Rivera — who does not turn 23 until next June — is projected by SoxProspects.com to return to Portland in 2026.