BOSTON (AP) — The Celtics traded point guard Kemba Walker to Oklahoma City for forward Al Horford, a person with knowledge of the deal told The Associated Press on Friday. It is Brad Stevens’ first major move since he moved from the Boston bench to the front office.

The Celtics will also send the No. 16 overall draft pick to the Thunder and receive center Moses Brown in return. The deal includes a swap of future second-round picks.

The person spoke on condition of anonymity because the deal had not been announced. The trade was first reported by ESPN.

Horford is returning to Boston and gives the Celtics the frontcourt presence they have lacked since he left two seasons ago. Horford was an All-Star and a member of the NBA All-Defensive team with the Celtics in 2017-18 while also posting the best assist numbers of his career.

Walker, 31, arrived in Boston in 2019 and helped the team reach the Eastern Conference finals in the NBA bubble last season. But knee injuries limited him to 43 games this year, and he missed the last two games of the first-round playoff loss to the Brooklyn Nets.

After playing his first nine seasons in Atlanta, Horford signed with Boston as a free agent in 2016 and led the team to the conference finals in his first two seasons. But he opted out of the team after three seasons to go to Philadelphia, then the 76ers traded him to the Thunder before last season.

Horford, 35, averaged 14.2 points and 6.7 rebounds this season, but he played just 23 games before the Thunder shut him down in late March to take a look at younger players — including Brown.

Brown, 21, was a first-team All-G-League selection this season, and the Thunder saw enough to call him up and award him a multiyear deal. The 7-footer averaged 8.6 points and 8.9 rebounds and tied a team record with 23 rebounds against the Celtics this season.

“As soon as he got his opportunity, he really embraced it,” Horford said during the team’s exit interviews. “He took it by storm. Playing in this league is not easy, night in and night out to have to prepare, everything that it takes, and I felt like he was up for the challenge.”