Denny Hamlin will miss six weeks with a compression fracture in his lower back.
Hamlin suffered the injury in a crash involving former Joe Gibbs Racing teammate Joey Logano on Sunday at Auto Club Speedway in Fontana, Calif.
Hamlin suffered an L1 compression fracture, but will not require surgery.
"If me getting back in a car was based on pain tolerance, then I would be in the car next week," Hamlin tweeted. "There's just more to it that I can't control."
NASCAR does not race this weekend, so Hamlin might miss only five races.
Logano and Hamlin collided on the final lap of Sunday's Auto Club 400, which was won by Kyle Busch.
After climbing out of his car, Hamlin immediately went to the ground. Rescue workers placed him on a stretcher and he was flown to a local hospital and stayed overnight.
"He probably shouldn't have done what he did last week, so that's what he gets," Logano said after the race, not knowing that Hamlin was hospitalized with the injury.
The two also made contact with their cars late during a race the week prior to Sunday at Bristol (Tenn.) Motor Speedway. That incident sent Logano into a wall. The two got into a shoving match afterward.
"That's a freaking genius behind the wheel of the 11 car," Logano said. "Probably the worst teammate I ever had, so I learned that now. He decided to run himself into the back of me, so, whatever. I have a scorecard and I'm not putting up with that."
Hamlin placed 25th on Sunday while Logano finished third.