Biffle, who will race in the premier Sprint Cup Series event, said he was hurt Tuesday night when he jumped from the dock to the boat and slipped in a wet spot. He banged his right side on the boat.
"I wish I had a better story, I really do," he said Friday at Bristol. "It's just one of those freak, stupid accidents where you take a fall and you have no way to stop it or brace it or grab because I was over top of water. You're gonna land on your ribs with all your weight, plus you jumped on top of it, so it was a stupid deal.
"I didn't do anything out of the ordinary. Everybody's jumped onto a boat before, but I just lost my footing."
Matt Kenseth will replace Biffle in Saturday's race, but Biffle plans to be in his car for the Sprint Cup race Sunday. Biffle is third in the Nationwide standings, 10th in the Sprint Cup Series.
Biffle decided to rest during the Nationwide event rather than risk aggravating his injury before Sunday's 500-mile main event.
"I'm just focusing on the Cup race because if you're bruised and if you get in a wreck in the Nationwide car, you blow a tire, you know how easy it is to get in a chain-reaction crash here," he said. "I'm thinking, "Why be even more sore for Sunday if something happened?' "
Biffle said he went to Roush Fenway Racing and sat in a race car to see how comfortable he was in the seat. He found it was more comfortable in the cockpit than it was in his personal vehicle.
"I actually feel better sitting in that (race car) seat because it's hard foam and it's molded. It doesn't create any pressure points," he said. "When you sit in a seat that has a lumbar support cushion, it's pushing in on you when you're naturally sitting in it like an easy chair or something, whereas this is hard and rigid and it fits your body."
