Celtics trade Kemba Walker, first-round pick to Thunder for Al Horford, Moses Brown

The trade comes after it was reported earlier this month that Walker and the Celtics mutually agreed to part ways this offseason. Walker was reportedly hurt by Danny Ainge's efforts to trade him in the past, and there was a rift in his relationship with Celtics management. 

Walker signed a four-year, $140 million contract with the Celtics prior to the 2019-20 season but struggled with injuries throughout his time in Boston. In 99 regular-season games for the C's, Walker averaged 19.9 points, 3.9 rebounds and 4.8 assists per game while shooting 42.3% from the field and 37.2% from deep. 

The 31-year-old still has two years remaining on his contract and is set to be paid more than $36 million next season and $37 million in 2022-23. 

Horford, meanwhile, returns to the Celtics after a year each with the Philadelphia 76ers and the Thunder. He didn't fit well with the Sixers, which prompted the franchise to trade him to the Thunder. The 35-year-old played just 28 games in 2020-21 before leaving Oklahoma in March after the Thunder could not find a trade partner for the veteran forward. 

Horford spent three seasons with the Celtics from 2016-19, averaging 13.5 points, seven rebounds and 4.6 assists per game while shooting 49.8% from the field and 38.2% from deep. 

Brown, 21, started 32 games for the Thunder this past season, averaging 8.6 points and 8.9 rebounds while shooting 54.5% from the field. 

The first-round pick that the Celtics are sending the Thunder gives Oklahoma City three first-round picks in the upcoming draft. The franchise also has an 11.5% chance of landing the No. 1 overall pick. 

Now that Walker is gone, the Celtics will likely search for his replacement. It's unclear whom they might be interested in.