The Boston Red Sox have signed right-handed reliever Garrett Whitlock to a four-year contract extension, the team announced Sunday.

Whitlock is guaranteed a total of $18.75 million from 2023 to 2026, a source told ESPN. The deal also includes club options for the 2027 and 2028 seasons, with the source saying Whitlock would make $8.25 million in 2027 and $10.5 million in 2028 if the options are picked up. The Red Sox could pay a $1 million buyout before 2027 or a $500,000 buyout before 2028, the source said.

After breaking into the majors with the Red Sox last season, Whitlock will remain eligible for Major League Baseball's new $50 million bonus pool for pre-arbitration-eligible players. He could earn bonuses based on innings pitched, awards and whether he serves as a starting pitcher or a reliever, making as much as $44.5 million over the life of the contract, the source said.

The 25-year-old had agreed last month to a one-year contract paying $720,000 while in the major leagues and $285,250 while in the minors.

"We hope we're just scratching the surface of what he can accomplish," Red Sox chief baseball officer Chaim Bloom said. "The fact that, he's said a few times, you give him the ball and he'll get outs until you take it from him, that's perfect."

Whitlock made 46 appearances for the Red Sox in his rookie season, going 8-4 with a 1.96 ERA and recording two saves. He threw 2 1/3 innings in his 2022 debut Friday, allowing a home run in a blown save during Boston's 6-5 extra-inning loss to the New York Yankees. Bloom said the sides agreed to the deal hours before Boston's season opener.

Among 30 rookies who pitched at least 70 innings last year, Whitlock ranked first in ERA, second in WHIP at 1.10 and third in opponent OPS at .631.

He began his pro career in the Yankees organization before undergoing Tommy John surgery in 2019 and being selected by the Red Sox in the 2020 Rule 5 draft.

When the 2020 minor league season was canceled because of the pandemic, he coached a travel-ball team and worked landscaping to make ends meet back home in Alabama. The Yankees left him unprotected the next offseason for the winter meeting draft, and Boston took a chance on him.

"Last year when they took me in the Rule 5 draft, it was an honor then, just because the fact they took a chance on me, everything like that," Whitlock said. "I just want to work my tail off."

The Associated Press contributed to this report.