Gregory Santos Bio
Gregory Omar Santos, born on August 28, 1999, is a Dominican professional baseball pitcher known for his work as a hard-throwing reliever in the San Francisco Giants organization. He has previously played in Major League Baseball (MLB) for the Chicago White Sox and Seattle Mariners, establishing himself as a bullpen arm at the highest level of the sport. Santos first signed with the Boston Red Sox as an international free agent in 2015 and has since climbed through several minor league systems before making his MLB debut.
Standing out as one of the younger Dominican pitchers to reach the majors in recent years, Santos has built his career on a power fastball and a willingness to handle high-leverage relief assignments. His path through the Boston Red Sox, San Francisco Giants, Chicago White Sox, and Seattle Mariners organizations reflects the modern international free agent pipeline, with stops at the rookie, low-A, and Triple-A levels before his first call to the big leagues.
Early Life and Background
Gregory Omar Santos was born in the Dominican Republic on August 28, 1999, growing up in a country with a deep tradition of producing Major League Baseball talent. From a young age, he was drawn to pitching, modeling his game on the power arms that frequently emerge from Dominican baseball academies. The Dominican Republic has long served as a primary source of professional baseball players, and Santos was identified early as a prospect with notable arm strength and a projectable frame.
As a teenager, Santos entered the international scouting market that connects young Dominican players with Major League organizations. His combination of size, velocity, and feel for pitching caught the attention of Boston Red Sox scouts, and at age 16 he was ready to begin his professional career. This early opportunity allowed him to develop within a structured organization rather than waiting for a traditional draft process.
Path to Professional Baseball
Santos signed with the Boston Red Sox as an international free agent on August 28, 2015, his 16th birthday, receiving a signing bonus of $275,000. He began his career in the Dominican Summer League, the typical entry point for young international players. In 2016, he posted a 3–3 record with a 4.17 ERA and 25 strikeouts over 41 innings for the DSL Red Sox, gaining valuable experience against older competition.
His development accelerated in 2017, when he made eight starts for the DSL Red Sox and went 2–0 with a 0.89 ERA and 24 strikeouts across 30 and one-third innings. That mid-summer performance was strong enough to draw trade interest, and on July 26, 2017, the Red Sox sent Santos and Shaun Anderson to the San Francisco Giants in exchange for veteran infielder Eduardo Núñez, shifting his development path to a new organization.
Gregory Santos Career
Early Career (2015-2019)
After joining the Giants organization, Santos split the remainder of 2017 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. In 2018, he moved to the United States for the first time and pitched for the Salem-Keizer Volcanoes of the Northwest League, posting a 2–5 record with a 4.53 ERA over 49 and two-thirds innings while earning Northwest League mid-season All-Star recognition.
The 2019 season saw Santos move up to the Augusta GreenJackets, where he went 1–5 with a 2.86 ERA over 34 and two-thirds innings before shoulder issues ended his season early. He did not return to game action in 2020 after the minor league season was canceled due to the COVID-19 pandemic. On November 20, 2020, the Giants added Santos to their 40-man roster to protect him from the upcoming Rule 5 draft.
San Francisco Giants Era (2021-2022)
Santos received his first major league call-up on April 22, 2021, and made his MLB debut that day against the Miami Marlins, pitching a scoreless inning of relief. He was the sixth-youngest player in the National League at the time of his debut and recorded his first two big league strikeouts, fanning Magneuris Sierra and Jazz Chisholm Jr. He was optioned back to the alternate site days later, then spent time with the Triple-A Sacramento River Cats and the Scottsdale Scorpions of the Arizona Fall League, where he was named an Arizona Fall League Rising Star.
On June 29, 2021, Santos was suspended 80 games after testing positive for the banned substance Stanozolol, keeping him off the mound for a significant stretch. He returned in 2022 to pitch across Sacramento and the ACL Giants Black, going a combined 1-2 with one save and a 4.63 ERA in 35 appearances. He made two brief relief appearances for the Giants in 2022 before being designated for assignment on December 19, 2022, following the Giants’ signing of Sean Manaea.
Chicago White Sox Era (2023)
On December 22, 2022, the Chicago White Sox acquired Santos from the Giants in exchange for minor league pitcher Kade McClure. Santos earned a full-season role in the White Sox bullpen in 2023 and appeared in 60 relief games, recording a 3.39 ERA with 66 strikeouts and 5 saves across 66 and one-third innings. His work as a high-leverage reliever helped stabilize the Chicago bullpen during the 2023 season.
Seattle Mariners Era (2024-2025)
On February 3, 2024, the White Sox traded Santos to the Seattle Mariners in exchange for right-handed pitcher Prelander Berroa and outfielder Zach DeLoach. He began the 2024 season on the injured list with a right lat strain, was transferred to the 60-day injured list on April 25, and was activated on July 8. In eight appearances for Seattle that year, he posted a 4.91 ERA with six strikeouts over 7 and one-third innings.
Santos made eight more appearances for the Mariners in 2025, compiling a 1-1 record and a 5.14 ERA with no strikeouts over seven innings. On April 25, 2025, he was placed on the 15-day injured list due to right knee inflammation, and it was announced that he would require cleanup surgery to repair cartilage. He was transferred to the 60-day injured list on April 29, 2025, and on November 21 he was non-tendered by Seattle and became a free agent.
San Francisco Giants Second Stint (2025-Present)
On December 17, 2025, Santos signed a minor league contract with the San Francisco Giants, returning to the organization where he first reached the major leagues. The signing offered him a chance to compete for a bullpen role in spring training and rebuild his career after injury-plagued seasons in Seattle.
Notable Events and Milestones
Among the signature moments of Santos’s career, his MLB debut on April 22, 2021, stands out, as he became the sixth-youngest player in the National League that day. He recorded his first two major league strikeouts in that game, punching out Magneuris Sierra and Jazz Chisholm Jr. He was also named an Arizona Fall League Rising Star in 2021 and earned Northwest League mid-season All-Star honors in 2018.
Gregory Santos Family
Family Background and Racing Lineage
Little is publicly known about Gregory Omar Santos’s immediate family or his specific upbringing in the Dominican Republic, as his parents and siblings have largely remained out of the public eye.
Personal Life
Santos has kept his personal life private, and there are no confirmed public details about a spouse or children.
2025 Season Performance
Santos’s 2025 season was cut short by injury after he was placed on the 15-day injured list on April 25, 2025, due to right knee inflammation that required cleanup surgery. He was transferred to the 60-day injured list on April 29, and over the course of the season he made just eight appearances for Seattle, going 1-1 with a 5.14 ERA and no strikeouts over seven innings of work. The injury marked a sharp contrast to his 2023 success with the White Sox and limited his ability to contribute to the Mariners’ bullpen.
On November 21, 2025, the Mariners non-tendered Santos, making him a free agent for the first time in his career. Just over three weeks later, on December 17, 2025, he signed a minor league contract with the San Francisco Giants, the team where he originally reached the majors. The deal provided Santos a familiar organizational home and an opportunity to compete for a bullpen role in the Giants’ system during the upcoming season.