"Danny Ainge needs to shut the f--- up and manage his own team," Riley said in a statement released through a Heat spokesman. "He was the biggest whiner going when he was playing and I know that because I coached against him."
Ainge said he was at a loss to explain why Riley should have gotten into such a lather in the first place.
"I stand by what I said. That's all. I don't care about Pat Riley. He can say whatever he wants," Ainge said in the runway shortly before Friday night's game against Atlanta.
Ainge couldn't let it go without one final shot at Riley.
"I don't want to mess up his Armani suits and all that hair goop. It would be way too expensive for me," he said.
"I think the referees got the calls right. I don't think it was a hard foul," Ainge said Thursday. "I think the one involving LeBron against [Carlos] Boozer, that was flagrant. I think the officials got it right.
"I think that it's almost embarrassing that LeBron would complain about officiating."
Ainge quickly responded to Riley later Friday.
"Pat Riley's right," he said. "I should manage my own team. I complained a lot to the officials. And I'm right, LeBron should be embarrassed about how he complains about the calls he gets."
Celtics coach Doc Rivers found Riley's comments "funny."
"Very interesting. I think it's cool. They should duke it out," Rivers said, laughing, according to the team's Twitter account.
Asked if Rivers believes Riley's statement could further stoke the Miami-Boston rivalry, Rivers noted, "Not unless they are playing. Really, I just think it's talk both ways. I'll let those two grown men handle their own grown-men argument. I'm going to stay out of it. On a side note, it just gives me a smile and it's interesting. I think it's fun. It's a flashback."
Riley, while presiding as the head coach of the Los Angeles Lakers, coached against Ainge in the 1984, 1985 and 1987 NBA Finals.
Information from ESPNBoston.com's Chris Forsberg and Peter May was used in this report.