Denny Hamlin has cited that the surgery needs to be done because his knee has buckled several times causing more damage. He plans to continue to race after the surgery and at least start "if they can pry him from the seat" to collect those valuable points and have Casey Mears as his back-up driver for if and when he gets out of the car.
Hamlin still remains optimistic about making the Chase though, "It’s not going to change our goals," he said. "If we don’t get in [the Chase], then it has to do with a lot of performance over the year, not just [the first few races after the surgery]."
My question in all of this is why didn't he make this decision during the off-week? Unless that is when he damaged his knee even more. I'm sure that question will be asked of him later, I know I'd be asking it.