Seranthony Domínguez

Seranthony Ambioris Domínguez Taveras (born November 25, 1994) is a Dominican professional baseball pitcher for the Seattle Mariners of Major League Baseball (MLB). He has previously played in MLB for the Philadelphia Phillies, Baltimore Orioles, Toronto Blue Jays, and Chicago White Sox.

Domínguez signed with the Phillies as an international free agent in 2011 and made his MLB debut in 2018. He underwent Tommy John surgery in 2020, then returned to pitch in the 2022 World Series. Philadelphia traded him to Baltimore during the 2024 season. He was dealt to Toronto during the 2025 season, with whom he won Game 1 of the World Series for the second time in his career. He signed as a free agent with the White Sox in 2026, then was dealt before the trade deadline to the Mariners.

Domínguez pitched for the Dominican Republic in the 2026 World Baseball Classic.

Early life Domínguez was born in Esperanza Valverde Mao, Dominican Republic. Of his unusual first name, Baseball America reported: "'I'm not sure where it comes from,' [he] said with a laugh. 'I think it’s something my parents heard on TV.'"

Career Philadelphia Phillies Minor leagues Domínguez signed with the Philadelphia Phillies as an international free agent in October 2011 for $25,000 . He led the DSL with two shutouts and complete games. In 2014, he played for the rookie-level Gulf Coast League (GCL) Phillies, going 2–2 record with a 3.12 ERA and 24 strikeouts in 26 relief innings pitched. That off-season, the Phillies organization told him he was being converted into a relief pitcher.

Domínguez began 2018 with the Double-A Reading Fightin Phils, going 1–2 with a 2.08 ERA with 18 strikeouts in 13 innings in 8 games, averaging 12.5 K/9. He was promoted to the Triple-A Lehigh Valley IronPigs in late April and went 1–0 with a 0.00 ERA in three games. He became the only major league reliever in recorded baseball history (dating back to 1908) to record at least two outs and allow no runs, hits, or walks in his first five major-league appearances. He also became the first pitcher in recorded history to not allow a run, hit, or walk in his first six appearances. He recorded his first career save against the St. Louis Cardinals on May 19, and his first win on May 26. Domínguez tied the all-time record for most perfect appearances (8) in a pitcher's first 11 games and pitched more innings in those games (10) than any of the other pitchers with whom he was tied. His 0.65 WHIP through the All-Star break (min. 30 IP) was the lowest ever by any Phillie. Domínguez ranked in the top 25 in MLB (minimum 50 innings) in both strikeout rate and in ground-ball rate. He struck out 32% of batters, best among rookies with at least 55 innings pitched. He also limited all batters to a .156 batting average and 0.93 WHIP (each fourth-best among National League (NL) relievers with 50 or more innings pitched), and batters to a .163 batting average in “high-leverage” situations, as calculated by Baseball Reference. Batters had a 66.4% contact percentage against him, second-lowest in the NL among pitchers with at least 50 innings pitched. His 16 saves tied Jack Meyer (1955) for the most by any Phillies rookie reliever. His season ended early with him on the injured list, due to a damaged ulnar collateral ligament in his right elbow.

Domínguez underwent Tommy John surgery on July 30, 2020, more than a year after he was initially placed on the injured list. On February 17, 2021, he was placed on the 60-day injured list as he continued to recover. On September 1, Domínguez was activated off the injured list. He returned to the majors in October, pitching one scoreless inning on October 3.

In the 2022 regular season, Domínguez was 6–5 with nine saves and a 3.00 ERA, as in 54 innings he struck out 61 batters over 54 relief appearances. That season, he had a 3.78 ERA and struck out 48 batters in 50 innings and 57 appearances. He missed time in June and July due to an oblique strain. He made six appearances in the 2023 postseason, allowing no runs and striking out 7 hitters in innings. Domínguez made 25 appearances down the stretch for Baltimore, posting an 0–2 record and 3.97 ERA with 28 strikeouts and 10 saves across innings pitched. He had two scoreless outings in the American League Wild Card Series.

Toronto Blue Jays On July 29, 2025, in between a doubleheader between the Orioles and Toronto Blue Jays, Domínguez and cash were traded to the Blue Jays for pitching prospect Juaron Watts-Brown. During the second game of the doubleheader, Domínguez tossed a scoreless inning against his former team. Domínguez pitched in 24 games for Toronto, logging a 2–1 record and 3.00 ERA with 25 strikeouts over 21 innings pitched. Domínguez went 2–0 in the postseason, winning Game 1 of the World Series but blowing a save in the seventh inning of the 18-inning Game 3.

Chicago White Sox On January 29, 2026, Domínguez signed a two-year, $20 million contract with the Chicago White Sox. Domínguez made 43 appearances for the White Sox, compiling a 4–3 record and 3.99 ERA with 47 strikeouts and 12 saves across innings pitched.

Seattle Mariners On August 1, 2026, the White Sox traded Domínguez, Nolan Jones, and Boston Smith to the Seattle Mariners in exchange for Luis Castillo. Domínguez gave up two home runs and four runs in his first outing for the Mariners.

International career Domínguez pitched for the Dominican Republic national team in the 2026 World Baseball Classic. He was 1–0, pitching four scoreless innings in four games as his team finished third.

Personal life Domínguez and his wife have two sons.