Horford is not going to Celtics. Pistons cleared cap space to give him max as well and meeting with him this weekend. And Pistons makes WAAAAAAAAAY WAAAAAAAY more sense than Celtics for big Al if he doesn't go to OKC or stays in Atlanta.
Both Celtics and Pistons become the #2 team in east easily with big Al. But Pistons is big Al's hometown team, he was raised in Michigan and his family is all here. His long-time agent Arn Tellem now officially works in the Pistons front office. Big Al's long time agent who quit to work for Pistons this year is expected to be leading the charge on selling Al on Pistons when they meet this weekend after all.
Absolutely no chance Big Al would pick Boston over Pistons. Would make no sense.
Only 3 teams have a chance at Horford. Atlanta, OKC, and Detroit. I say Atlanta is still the most likely option, they can pay him the most.