Charlie Kimball has been diagnosed with a fracture of the fifth metacarpal of his right hand after what his team described as "a freak incident" during testing for the IZOD IndyCar Series at Mid-Ohio Sports Car Course on Thursday.

Kimball had a light spin off the track during the session that sent him off the track and into the tyre barriers.

"When he took off his hands off the steering wheel, the knock against the tyre barrier reversed the steering wheel," explained Mike Hull, general manager for Chip Ganassi Racing for whom Charlie Kimball drives the #83 Novo Nordisk entry. "One of the corners hit the back of his hand when it snapped back."

Kimball was sent to the nearby MedCentral Hospital in Mansfield Ohio for further tests and evaluation of his hand, and will be re-evaluated by an Indianapolis specialist on Friday.

The injury is not thought to be serious and should not affect Kimball's participation at the next event of the season, the Honda Indy 200 at Mid-Ohio on August 5.

In all, 24 of the 25 regular entries were in action at the track on Thursday. Only HVM Racing's Simona de Silvestro missed out on taking to the 2.258-mile 13-turn road course.

The full day's testing was shortened by 90 minutes because of a thunderstorm, but otherwise proved highly productive - with times said to be already between one and two seconds faster than the pole time seen for last year's race.

"The new car is quick without even putting red tyres on," said Scott Dixon, one of the other drivers in the Chip Ganassi stable. "I can't wait until next weekend," he added.

Dixon's pole time in 2011 - using the old chassis and engine specifications - was 1:08.0776s. He went on to win the race and set the fastest lap in the process, explaining his eagerness to get back in action there next weekend.