Per ESPN's Adrian Wojnarowski, the Thunder are going to keep Horford out of games for the rest of this season as they build around their young players.
Wojnarowski noted Oklahoma City will explore trade opportunities for the five-time All-Star during the offseason.
Horford issued a statement about the decision, via Wojnarowski:
"I know what it's like to be a young, aspiring player, and at this point in the season I understand how important playing meaningful minutes is for their careers and their development. ... I look forward to supporting the guys who supported me.... When I arrived, I understood the direction of the team, we had a great individual plan in place for me, and I feel like as a result I've played really good basketball for the Thunder."
Even though Horford won't appear in games, Wojnarowski noted he will continue to train at the Thunder facility.
The key to that deal may have been the inclusion of a 2025 first-round draft pick. General manager Sam Presti has been stockpiling picks, especially since trading Paul George to the Los Angeles Clippers in July 2019.
The Thunder could have multiple first-round draft picks in each of the next six drafts.
Even though Oklahoma City is in the midst of a rebuild, the team has played respectable basketball this season. The Thunder are 13th in the Western Conference, but their 19-25 record is only the eighth-worst in the NBA.
Horford is owed $53.5 million over the next two seasons. The 34-year-old averaged 14.2 points on 45.0 percent shooting, 6.7 rebounds and 3.4 assists in 28 starts for Oklahoma City this season.