A right-hander who turns 32 next month, Baez was 7-2 with a 3.10 ERA in 71 relief appearances last season, striking out 69 in 69 2/3 innings while walking 23. He had a $2.1 million salary last year and is eligible for free agency after this season.
Arbitrators Robert Herman, Jeanne Charles and Margaret Brogan made the decision Wednesday, a day after hearing arguments.
Boston pitcher Eduardo Rodriguez argued his case Wednesday, asking for a raise to $8,975,000 rather than the $8.3 million offer of the Red Sox. A right-hander who turns 27 in April, Rodriguez was a career-best 19-6 with a 3.81 ERA in 34 starts last season, when he made $4,325,000. He is eligible for free agency after the 2021 season.
The case was heard by Steven Wolf, Walt De Treux and Melinda Gordon, who are expected to rule Thursday.
Eight players remain scheduled for hearings, which run through Feb. 21.