Juan Pablo Montoya has appealed for time to impress after making his first Nascar test run on Monday at Alabama's Talladega Superspeedway track.
"I think a lot of you are expecting me to win my very first race, but I don't think that's going to happen," he said.
"It's going to take time," said the Colombian, who admitted that his first Nascar run had been exhilarating.
"It was like 'Oh, my God'. I came out of the pits and went full throttle. It felt quick," said the former F1 star.
Montoya could make his Nascar debut for the Ganassi team at the same track next month after being released from his Formula One contract with McLaren.
"I'm 100% committed to this, and this is the only thing I'm going to be doing," he said.
"I think you have to have a very open mind about it. It's going to be difficult and it's going to be a challenge."
Montoya was dropped from McLaren in July after making public his deal to join Nascar.
But McLaren refused to release him from his contract, preventing him from testing for Ganassi until now.