Dreyer and Reinbold driver Justin Wilson has been diagnosed with a fractured bone in his back, following an incident in Saturday morning practice ahead of the Honda Indy 200 at the Mid-Ohio Sports Car Course.

The Sheffield-born driver - whose younger brother Stefan is also competing in the Indy Lights support series - appeared to come close to the tyre barrier when running wide at high speed through turn 1, and then bounced heavily over the uneven surface across a service road and briefly launched into the air.

Wilson subsequently used Twitter to describe the accident as he saw it from the driver's seat: "I dropped 2 wheels off on exit of one then bottomed out on service road," he wrote. "Then coasted to a stop as I knew I had done something to my back. I think the service road was not level with the grass. Sent car airborne."

The #22 car came to a halt in turn 1 - triggering a full course yellow - at which point Wilson removed the steering wheel and appeared to be about to get out, before slumping back in evident pain. The IndyCar safety team was on the scene to extricate him using a next brace and backboard and he was dispatched to nearby Mansfield MedCentral for evaluation.

Tests confirmed that Wilson had sustained an anterior compression fracture of his fifth thoracic vertebrae because of the violence of the car's travel over the uneven surface through turn 1.

"There is talk of him flying back to Indianapolis for further evaluation," said team owner Dennis Reinbold, so that Wilson can be under the care of IndyCar's lead medical consultant Dr Terry Trammell.

Wilson was back on Twitter in the evening to update his fans. "Thanks for all the messages. I appreciate the support. This morphine stuff works well although I keep falling asleep while writing," he wrote.

"I fly to Indy tomorrow," he said, confirming his team boss's earlier thoughts. "They think I won't need surgery but I will need a brace. I will be back as soon as possible."

With only a little over two months to go for recuperation until the end of the 2011 season at Las Vegas, there are concerns that the injury could put Wilson out of the car for the remaining six races of the year, depending on the severity of the break and the need for surgery.

Dario Franchitti voiced the concern of many drivers about what had happened to Wilson and to the suitability of the circuit through turn 1 for IndyCar competition. "It was pointed out last week when we were at the test. It's been a problem there for a long time, but with the new owners, they haven't had time yet to implement a lot of the stuff they want to do," he said.

"The grass is very, very rough," he explained. "Massive undulations on the grass. Then you swap onto an access road almost, another part of the track, then it goes back onto the grass. The difference can be as much as a foot in places. Especially there, you're fourth gear, I don't know what the speed is in miles an hour, but it's bloody quick. The cars don't deal with that kind of rough ground."

With little time to put in place contingency arrangements, the Dreyer and Reinbold Racing team turned to Simon Pagenaud as an emergency substitute, the French sportscar star having been spectating at the event after taking part in last week's test session at Mid-Ohio with Sam Schmidt Motorsports. Pagenaud has already been a replacement driver for DRR back in April when he sat in for Ana Beatriz after she suffered wrist injuries and had to miss the Grand Prix of Alabama at Barber Motorsports Park.

"I feel really sorry for Justin, he's a good friend and you never wish for this kind of situation to happen," said Pagenaud. "I'm glad that Dreyer & Reinbold Racing asked me to represent him and the team. I'm pleased that they have confidence in me to do the job."

Considering Pagenaud had only about 90 minute to prepare and had to beg, borrow and scrape together equipment (and even a race seat) from up and down pit lane, Pagenaud did impressively well to qualify 18th in the 27-car field.

"All in all, the car was really good in qualifications," he said. "I think the car is very well setup by Justin and the team. I was a bit cold turkey going in, so I'm pretty pleased with the performance and we were only a tenth off of transferring to the next session."