The St. Louis Cardinals have added a towering left-handed arm to their organization, acquiring Eduardo Rivera from the Boston Red Sox in exchange for 18-year-old right-hander Juan García.
The trade, first reported by SoxProspects.com’s Andrew Parker, gives the Cardinals a 23-year-old pitcher who has already reached the major leagues and still carries remaining minor-league options.
Rivera, a native of San Juan, Puerto Rico, stands 6-foot-7 and weighs 237 pounds. Originally drafted by the Oakland Athletics in the 11th round of the 2021 draft out of high school in Carolina, he signed with Boston as a minor-league free agent in June 2024.
He made his MLB debut with the Red Sox on April 22, 2026, working 3 1/3 scoreless innings in relief against the Yankees.
Across four appearances for Boston this season, he posted a 0-1 record with a 6.30 ERA in 10 innings, striking out 10 while walking six. He finished the year on the injured list with a lumbar strain.
In the minors, Rivera showed more encouraging results.
Across 55 2/3 innings at the upper levels, he struck out roughly 30 percent of the batters he faced while posting a solid earned-run average, though an elevated walk rate remained a clear area for refinement.
His fastball sits in the mid-90s and he pairs it with a promising slider.
The combination of size, velocity, and remaining options makes him a flexible piece who can be developed either as a multi-inning reliever or a starter without immediately occupying a 40-man roster spot.
For the Cardinals, the acquisition fits a familiar pattern of adding controllable pitching depth at modest cost. Rivera arrives with major-league experience yet is still young enough that any development gains can be realized within the organization.
The club parts with García, a Mexican-born right-hander who spent the 2026 season in the Dominican Summer League.
Signed as an international free agent in January 2025, García made 11 starts for the DSL Cardinals, posting a 4.40 ERA over 43 innings with 39 strikeouts. While he is still years from the majors, he represented a projectable arm in the lowest levels of the system.
The trade comes days after the Red Sox designated Rivera for assignment, clearing a spot on their 40-man roster. Boston’s bullpen already features several left-handed options, which likely made Rivera expendable.
St. Louis, by contrast, gains a lefty with swing-and-miss traits who can be optioned freely while the organization evaluates his role.
Whether Rivera ultimately settles into a relief role or continues developing as a starter, the Cardinals have secured a high-ceiling arm without surrendering a prospect close to contributing at the major-league level. The move adds another body to a pitching group that values both present depth and long-term upside.
