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Indianapolis — Ruled out of racing indefinitely, IndyCar driver James Hinchcliffe thanked the "heroes" who helped him after his frightening crash at Indianapolis Motor Speedway.

His girlfriend, Kristen Dee, said he was awake and communicating Tuesday morning, less than 24 hours after undergoing surgery on his left thigh.

Two sources familiar with the details told The Associated Press his leg had been pierced by the car's right front rocker. The surgery at Indiana University Methodist Hospital was needed to stop massive bleeding.

"He's stable and improving," said Dr. Timothy Pohlman, who performed the surgery. "His condition was critical upon his arrival and I think the IndyCar system as a whole needs to be commended for how well they can take care of drivers in this situation."

Hinchcliffe said in a statement released by IndyCar: "Words can't describe how thankful I am" to the on-track Holmatro safety team. "Those guys, in addition to the doctors and staff at the hospital, are my heroes. I can't say enough how much I appreciate the outpouring of support from IndyCar fans, my family and fellow drivers. We are all one big family and it feels like that today."

Hinchcliffe lost a significant amount of blood, a person with knowledge of the injury told The Associated Press on condition of anonymity because the details have not been released by IndyCar or Schmidt Peterson Motorsports.

Honda said Hinchcliffe's right front suspension failed, and the driver was sent hard into the third turn wall during practice for Indianapolis 500.

It was the fifth crash in a scary week, and IndyCar huddled with Honda and Chevrolet to determine whether new aerodynamic kits installed on the cars were causing problems ahead of its showcase race on Sunday. They eliminated the extra horsepower the cars were supposed to have for qualifying, which was also turned into a non-points chase.