This Story First Appeared in the Digital Edition of The Boston Globe

 

After Kyrie Irving left Boston as a free agent two years ago, the Celtics thought they had found the perfect replacement when they signed another All-Star point guard, Kemba Walker, to a four-year maximum salary deal.

But Walker’s past two seasons have been marred by a persistent left knee issue, and now his time in Boston has come to an end.

 

The Celtics have agreed to send Walker, the No. 16 pick in next month’s draft, and a 2025 second-round pick to the Thunder in exchange for former Celtics forward Al Horford, center Moses Brown and a 2023 second-round choice, a league source confirmed.

 

It is the first massive transaction of Brad Stevens’s tenure as Boston’s president of basketball operations.

Walker, who averaged 19.3 points, 4.9 assists and 4 rebounds this season, has two years and $73 million remaining on the four-year deal he signed in the summer of 2019. He missed the first 11 games of this season to strengthen his left knee, and did not play in games on back-to-back nights all year.

 

His departure will create some future financial flexibility for the Celtics, who also received a bit of a break when Jayson Tatum failed to make an All-NBA team, costing him about $5 million per season in the extension that kicks in next year.

 

Horford has $53 million left on the four-year deal he signed with the 76ers two seasons ago. His first season in Philadelphia did not work out, however, and he was traded to the Thunder last year. He played in 28 games with Oklahoma City last season before the team deactivated him so it could focus on developing its younger players who are part of its future.

 

Brown, 21, parlayed a two-way contract with the Thunder into an NBA deal in March, one day after erupting for 21 points and 23 rebounds in Oklahoma City’s loss to the Celtics. He averaged 8.6 points, 8.9 rebounds and 1.1 blocks per game this season.