Photo: Greg M. Cooper/USA TODAY Sports

Boston Celtics made the first trade of the offseason as they traded Kemba Walker to the Oklahoma City Thunder, per Adrian Wojnarowski of ESPN.

The Celtics’ new president of basketball operation Brad Stevens gave up the No. 16 overall pick in the 2021 draft and a 2025 second-round draft pick to Oklahoma City for Al Horford, Moses Brown and a second round pick.

The trade means that the Celtics secure financial flexibility for the future in addition to welcoming back Al Horford, who left Boston in the 2018-19 season to sign a lucrative deal with Philadelphia.

To sweeten the deal, the Celtics included their first-round pick (No. 16) in next month’s NBA Draft, as well as a 2025 second-round pick.

Oklahoma City included Moses Brown in the trade. Brown had an excellent year in the G League spending time with the Blazers and Thunder on two-way contracts.

Brown was named to the All-NBA G League First Team after season averages of 18.5 points, 13.9 rebounds and 1.9 blocks in 26.4 minutes per game.