Sprint Cup driver Denny Hamlin is expected to miss six weeks with a compression fracture in his lower back, Joe Gibbs Racing announced Tuesday night.
Hamlin was injured in a last-lap crash involving former Joe Gibbs Racing teammate Joey Logano on Sunday at Auto Club Speedway.
After an evaluation by Dr. Jerry Petty of Carolina Neurosurgery & Spine Associate, it was determined that Hamlin suffered an L1 compression fracture. Hamlin will not require surgery, but recovery time is estimated at six weeks.
"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."
With NASCAR being off this weekend, Hamlin might miss five races. However, the time off will put Hamlin, 10th in points, in serious jeopardy of missing the Chase for the first time in his seven Cup seasons unless he can make it as a wild card on wins inside the top 20. Jimmie Johnson is the only other driver never to miss the Chase since it was implemented in 2004.
Roger Penske said Wednesday that Logano and Hamlin have exchanged text messages since their crash. He said he didn't know what Logano, one of his drivers, and Hamlin said to one another.
"It didn't go well," Hamlin told The Associated Press. "The conversation was both short and unproductive."
"I've texted back and forth with [Hamlin] and said that we're thinking about him," Penske said. "Obviously, we're hoping for a speedy recovery. It's never good to have a driver out for a period of time."
No decision has been made on a replacement driver for Hamlin during his absence from the NASCAR Sprint Cup Series, Joe Gibbs Racing announced.
One potential candidate to replace Hamlin is Elliott Sadler, who drives Nationwide for JGR. Sadler is a former full-time Cup driver who has won three times in the Sprint Cup series.
In Sunday's race, Hamlin's car hit the inside retaining wall head-on after being spun by Logano on the final lap. Hamlin's car hit a small portion of the track where the SAFER barriers designed to reduce impact did not cover the concrete wall.
Hamlin climbed out of his car and immediately collapsed. He was carried off on a stretcher and then airlifted to a nearby hospital.
Before Fontana, the two nearly came to blows at Bristol after Hamlin spun Logano while Logano chased Jeff Gordon for a late lead. Logano yelled into Hamlin's car after the race, sparking a brief confrontation between their teams.
Then came the wreck in California, and the presumption that Logano had contact with Hamlin as payback. Penske doesn't buy it.
"These guys are racing hard, and it's the last lap and it's just the way the cars got together," Penske said. "The way Denny hit the wall was very unfortunate. ... It's never good to have a driver out for a period of time."
Hamlin has a history of back injuries. He sat out the Nationwide Series race at Daytona International Speedway last season because of back spasms from an incident at Kentucky. He told reporters then he had bulging disks in his back.
Information from ESPN.com's David Newton and The Associated Press was used in this report.