But it appears the C's were even more upset with the events that led up to Horford signing a four-year, $109 million deal with Philadelphia. Horford recently stated he was "surprised" by the Sixers' interest, but the Celtics reportedly believe teams had deals on the table for Horford before free agency even began, ruining their chances of re-signing the 12-year veteran.
On the latest Hoop Collective Podcast, ESPN's Brian Windhorst said Boston complained about teams tampering in their pursuit of Horford.
"I don't know if you heard this, but the Celtics were, from what I am told, one of the teams that kind of stomped their feet about what they felt was tampering," Windhorst told co-hosts Jackie MacMullan and Tim MacMahon. "Not with Kyrie, although that looked like it was lined up pretty far in advance, but with Horford.
"What happened with Horford, again from what I'm told, really upset the Celtics. They were thinking they were going to be able to negotiate with him. Talk to him about a new contract and all of a sudden it was like he already knew what his market was and he was out of there."
If Danny Ainge felt there was some foul play involved in Horford's free agency, he hasn't expressed it publicly. The C's general manager attributed Horford's decision to it simply being a "different era" in the NBA.
Regardless of what may or may not have gone down in teams' pursuits of Horford, the Celtics rebounded quickly after his departure by signing eccentric big man Enes Kanter and re-signing Daniel Theis to a two-year contract.
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NBA Rumors: Celtics felt teams tampered in pursuit of Al Horford originally appeared on NBC Sports Boston