Boston Red Sox Santos signed with the
Boston Red Sox as an international
free agent on August 28, 2015, for $275,000. He spent the 2016 season with the
Dominican Summer League Red Sox, going 3–3 with a 4.17 ERA and 25 strikeouts over 41 innings. Santos made 8 starts for the DSL Red Sox in 2017, posting a 2-0 record and 0.89 ERA with 24 strikeouts across innings pitched.
San Francisco Giants 2017–2019 On July 26, 2017, Santos and
Shaun Anderson were traded to the
San Francisco Giants in exchange for
Eduardo Núñez. He split the 2017 season between the DSL Red Sox and the
Dominican Summer League Giants, going a combined 3–0 with a 1.29 ERA and 41 strikeouts over 49 innings. He played for the
Salem-Keizer Volcanoes in 2018, posting a 2–5 record with a 4.53 ERA over innings, and was named a
Northwest League mid-season All Star. He played for the
Augusta GreenJackets in 2019, going 1–5 with a 2.86 ERA over innings. Santos missed the second half of the 2019 season due to shoulder issues.
2020–2022 Santos did not play in a game in 2020 due to the cancellation of the minor league season because of the
COVID-19 pandemic. On November 20, 2020, Santos was added to the
40-man roster, in order to be protected from the
Rule 5 draft. On April 22, 2021, Santos was promoted to the major leagues for the first time. He made his MLB debut that day against the
Miami Marlins, pitching a scoreless inning of relief, and was the 6th-youngest player in the NL. In the game, he also notched his first two major league strikeouts, punching out
Magneuris Sierra and
Jazz Chisholm Jr. On April 28, Santos was optioned to the Giants' alternate site in Sacramento to make room for new outfielder
Mike Tauchman. He later began his minor league season with the Triple-A
Sacramento River Cats. On June 29, 2021, Santos was suspended 80 games after he tested positive for the banned
androgen and
anabolic steroid Stanozolol. He played in 2021 for the
Scottsdale Scorpions, for whom he was 0–1 with a 4.15 ERA in 10 relief appearances, and was named an
Arizona Fall League Rising Star. In 2022 with the Giants he made two relief appearances, and in 3.2 innings gave up 3 hits, 3 walks, and had two strikeouts.
Chicago White Sox On December 22, 2022, Santos was traded to the
Chicago White Sox for minor league pitcher
Kade McClure.
Seattle Mariners On February 3, 2024, the White Sox traded Santos to the
Seattle Mariners in exchange for right-handed pitcher
Prelander Berroa, outfielder
Zach DeLoach, and a Round B Competitive Balance draft pick, which was used to draft Blake Larson. He began the year on the
injured list with a right
lat strain. Santos was transferred to the 60-day injured list on April 25. He was activated from the injured list on July 8. In eight appearances for Seattle, Santos recorded a 4.91 ERA with six strikeouts across innings pitched. Santos made another eight appearances for the Mariners in 2025, compiling a 1-1 record and 5.14 ERA with no strikeouts over seven innings of work. On April 25, 2025, Santos was placed on the 15-day injured list due to right knee inflammation; it was announced that he would require a cleanup surgery to repair cartilage. He was transferred to the 60-day injured list on April 29. On November 21, Santos was non-tendered by Seattle and became a free agent.
San Francisco Giants (second stint) On December 17, 2025, Santos signed a minor league contract with the
San Francisco Giants. He was assigned to the Triple-A
Sacramento River Cats to begin the regular season, recording a 2.45 ERA with six strikeouts and three saves over eight appearances. On April 29, 2026, the Giants selected Santos' contract, adding him to their active roster. ==References==