CHARLOTTE, N.C. — Three-time NASCAR champion Tony Stewart underwent a second surgery on his broken right leg in North Carolina on Thursday and remains hospitalized under observation.

The surgery was to insert a metal rod inside the tibia, and Stewart-Haas Racing said a specialist pressed the tibia to its correct position.

Stewart broke both the tibia and fibula in his right leg Monday night in a sprint car race in Iowa. He underwent a first surgery in Iowa following the accident to clean and stabilize the injury.

Stewart is out indefinitely, and Max Papis will drive his No. 14 Chevrolet this weekend at Watkins Glen International, where Stewart is a five-time winner. It will bring Stewart's streak of 521 consecutive Cup starts to an end.

Stewart-Haas Racing has not named an interim driver for beyond this weekend, and said no discharge date has been decided for the 42-year-old driver/owner.

Stewart was leading with five laps remaining at Southern Iowa Speedway on Monday night when a lapped car spun in front of him, causing Stewart to hit that car and flip several times. He was taken from the track by ambulance.

It was the third sprint car accident he'd been involved in over the last month, but his passion for grassroots racing remained strong and he'd bristled just last week at Pocono Raceway when asked why he continued to put his day job at risk for his hobby.

"We all know Tony loves to do those races. We know that that's his golf game, that's his hunting, his fishing, all the things that the rest of us do," said Greg Zipadelli, the competition director at SHR. "I think it makes him better at what he does here, but it obviously leaves the door open for a situation that we're in now. I think that as many races as he's run in the past, we're probably lucky that this is the first time we're dealing with this."

"We'll do our best at Stewart-Haas to put pieces together and sit down and evaluate it," he added. "That doesn't mean anything other than we will talk about it, we'll discuss it and we'll try and do what's best for Stewart Haas and our partners in the future."

Stewart was 11th in the Sprint Cup standings with five races to go before the Chase for the championship, and won't race for a fourth title now. He's been under fire all this week for ruining that opportunity for his team and his sponsors, but his childhood idol A.J. Foyt defended him.

"He ain't no prima donna and life is short, and we don't know how we are going to die or what's going to happen," Foyt said. "I just hate to see anybody badmouth Tony for anything he's doing. If they are worrying about their jobs and him getting hurt, what's to say he won't have a heart attack tomorrow and die?"