The Philadelphia 76ers big man has played for Brad Stevens, though, and that experience gave him all the evidence he needs.
In a chat with the Boston Herald's Steve Bulpett over the weekend, Horford weighed in on his former team's hot start and said he's not surprised to see Stevens' group jelling so quickly.
"Coach, you know, he's going to put everyone in position to be successful," Horford said. "I mean, even the year that we were there that Kyrie and Gordon were missing and we had Shane Larkin starting or Semi (Ojeleye), he figured out how to do the most with what he had. So I'm not surprised by this."
When pressed on why Stevens couldn't make things work last season, Horford pointed to an overabundance of talent that led to chemistry issues.
"Last year was just too much," Horford added. "There were too many guys for coach to satisfy everyone."
Horford was one of five Celtics to average more than 27 minutes per night last season, and that group didn't even include Hayward or Jaylen Brown. That the 33-year-old decided to leave Boston for Philly in the offseason was a sign he saw the writing on the wall with Boston's crowded roster.
Horford apparently shares the same view as Celtics president of basketball operations Danny Ainge, who pointed to the "equal depth" on last season's squad as a potential cause of Boston's chemistry issues.
The new-look C's seem to be getting along quite well, though. They're 14-5 entering Tuesday and have the chance to avenge one of those five losses when they host Horford's Sixers next Thursday.
Don't miss NBC Sports Boston's coverage of Celtics-Heat, which tips off Wednesday at 7 p.m. with Celtics Pregame Live, and then Tommy & Mike have the call at 7:30 p.m. You can also stream the game on the MyTeams App.
Why Al Horford isn't surprised the Celtics already have strong chemistry originally appeared on NBC Sports Boston