The Clippers were leading by four at half time but Miami produced a fightback after the break to claim a 102-97 win at the AmericanAirlines Arena.
"You can see in the third quarter they slowed the game down and we slowed it down with them," Rivers told reporters. "And I thought that really hurt us.
"We had a six-minute stretch where we could have stretched the game. Instead we started walking it up, slowing everything down. They're too good with a set defense. We allowed them to set their defense. That's when all the turnovers came."
The Clippers have won three and lost three of their opening six games this season.