NBA rumors: Mavericks the favorites to sign Al Horford in free agency originally appeared on nbcsportsbayarea.com It appears Al Horford's time with the Celtics is coming to an end, and that could make things even worse for the injury-depleted Warriors. The big man opted out of the final year of his contract earlier this week, reportedly with the intention of signing a multi-year deal in Boston. But things went south Tuesday: And the Warriors can't be happy with where the five-time All-Star is rumored to end up.