"I'd say 50-50," Rivers said. "I just don't really know."
The Clippers played without the eight-time All-Star in Game 1 in Houston on Monday, and pulled off a 117-101 win.
"Even if we lost, that decision [for Game 2] wouldn't be different," Rivers said.
Paul sustained a strained left hamstring in the first quarter of the Clippers' 111-109 Game 7 win over the
Rivers said that hamstring strains are problematic because they are difficult to monitor and assess.
"That's an injury you just don't know, and it's an injury you can't do an X-ray and say that you're all right," Rivers said. "It's an injury where you've got to trust your player, which is the worst kind of trust in this situation."
The Clippers had a film session Tuesday, and Rivers said he planned to check in with Clippers' trainer Jasen Powell that evening.
"It's a hard injury for your trainer because he at some time is going to give you the thumbs up, and he's going to be sweating that whole night."
Rivers said that Paul was going to try and get some shots up Thursday.