Bello signed with the
Boston Red Sox as an international
free agent on July 2, 2017. He spent his first professional season in 2018 with the
Dominican Summer League Red Sox and
Gulf Coast League Red Sox. In 2019, he played in
Single–A for the
Greenville Drive, compiling a 5–10
win–loss record in 25 games, all
starts, with a 5.43
earned run average (ERA) while striking out 119 batters in
innings pitched. Bello started 2021 with Greenville before being promoted to the
Double-A Portland Sea Dogs. He was selected to the mid-season
All-Star Futures Game, and was named the Starting Pitcher of the Year within Boston's
farm system at the end of the season. Bello made six starts for Greenville and 15 starts for Portland, going a combined 7–3 with 3.87 ERA while striking out 132 batters in innings. Bello began the 2022 season with Portland. He was ranked 97th in the list of baseball's top 100 prospects by
Baseball America. On May 5, Bello threw a seven-inning
no-hitter in the second game of a
doubleheader against the
Reading Fightin Phils; it was the fifth no-hitter in Sea Dog history. Bello was promoted to the
Triple-A Worcester Red Sox on May 16. In his first nine games with Worcester, he posted a 6–2 record and a 2.81 ERA while striking out 72 batters in innings. On July 4, the Red Sox announced that Bello would be promoted to the major leagues for the first time. He made his major-league debut on July 6, starting against the
Tampa Bay Rays at
Fenway Park, taking the loss after allowing four runs on six hits in four innings. He made another start on July 11, then was optioned back to Worcester. Bello was selected to the 2022
All-Star Futures Game but replaced on the roster due to his major-league promotion. He was recalled by Boston on July 22. On August 4, he was placed on the
injured list with a left groin strain. He rejoined the team on August 24. On September 3, Bello tossed six scoreless innings against the
Texas Rangers, striking out five en route to his first major league victory. Overall with Boston during 2022, Bello pitched to a 2–8 record in 13 games (11 starts) while compiling a 4.71 ERA and striking out 55 batters in innings. Bello was named the minor-league Starting Pitcher of the Year by the Red Sox organization. Bello began the 2023 season on the injured list with right elbow inflammation. He was activated on April 17. After posting a 9.82 ERA in two starts, he was optioned to Worcester on April 24, then recalled on April 28 when
Garrett Whitlock was placed on the injured list. For the 2023 season, Bello appeared in 28 major-league games, all starts, and posted a 12–11 record with a 4.24 ERA while striking out 132 batters in 157 innings. On March 9, 2024, Bello signed a six-year, $55 million contract extension with the Red Sox including a seventh-year club option for $21 million. During
spring training, he was named the team's starter for
Opening Day of the 2024 season. Due to
lat muscle tightness, Bello was on the injured list from late April until being activated on May 12. On July 8, 2025, Bello tossed a
complete game against the
Colorado Rockies, recording the win in the 10–2 victory. ==See also==