The Penske Dodge driver crashed into a barrier head on at approximately 100mph following a suspected brake failure of his #2 car at Turn 1. Although he was able to exit the car under his own power, he was then airlifted to hospital for x-rays and checks and was expected to be released on Thursday afternoon.
Keselowski broke news of the accident and of his his progress in hospital through his Twitter account while fellow Sprint Cup drivers also testing at Road Atlanta - in preparation for the upcoming road course round at Watkins Glen - wrote with information and pictures.
Reigning champion Jimmie Johnson tweeted pictures of the barrier hit by his rival and also of Keselowski's car being lifted by a loader.
"In a serious accident today while testing road Atlanta. Hit wall head on in a 155mph corner after brakes failed. Airlifted to hospital," Keselowski wrote on his Twitter feed.
The 27-year-old also tweeted a pictures of his injuries, one of them showing swelling on his left ankle. However he expects to compete in this weekend's Sprint Cup event at Pocono, where he arrives 21st in the driver standings with a victoryat Kansas to his name.
