Biffle, a Sprint Cup Series regular, said he slipped and fell while attempting to jump from the dock to the boat. He said the slip resulted in his right side striking the edge of the boat. Biffle was boating with friends near his home in Charlotte, North Carolina.

"I wish I had a better story, Biffle said. "I jumped over to the dock and the boat was kind of drifting out a little bit...There was a little bit of dew in the air and the platform must have been wet, and when I jumped over it just shot my foot out from underneath me. It turned me around backwards and put me right on my side and on my back on the edge of the boat."

As a precaution, Biffle opted not to drive in the 300-lap race at Bristol, with Roush Fenway Racing teammate Matt Kenseth taking his place. Biffle and Kenseth have agreed to swap Nationwide races, with Biffle substituting for Kenseth in the No.16 Ford in an upcoming event this season.

"I feel pretty good now. I got in the car, just bruised, and the reason why I'm just focusing on the Cup race is 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. I'm thinking, 'Why be even more sore for Sunday if something happened'?"

Biffle, who is currently 10th in Sprint Cup points, is expected to compete in Sunday's Food City 500 at Bristol. He was 10th quickest of 45 drivers in Friday's practice. Biffle won the most recent Nationwide event on February 28 at Las Vegas, ending a 76-race winless streak in the series.