Moreno in for Gregoire

Frenchman Gregoire, 38, suffered a cracked vertebra in a huge crash during Thursday's official practice session and will be out of action for at least two months, giving the veteran Brazilian a shot at the race.

"I haven't known another driver than Stephan," team boss Tom Chastain said.

"He's the only driver I've ever known, but we need somebody with experience to come in here and do the job real quick. From what I've been told, Roberto is the guy that can get the job done."

Moreno, 48, who returned to single seaters this year in ChampCar after three years in GT racing, will get his first taste of action in Friday practice and then attempt to qualify the car for the race on 'bump day'.

Two-time IndyCar race-winner Alex Barron, was another driver to confirm his participation in practice as he has signed for Beck Motorsports.