Indy 500 winner Rossi had 'no idea' about ovals, boss Andretti says

Rossi stretched his fuel mileage in the final stint of Sunday's race and was elevated to the lead as others pitted.

He made it across the line to win as a rookie, then ran dry on the slowing-down lap.

Prior to his 2016 deal to switch to IndyCar with a joint Andretti and Bryan Herta Autosport entry, 24-year-old American Rossi had spent the majority of his career in European racing and did not visit the Indianapolis Motor Speedway until Easter this year.

"He had no idea," Andretti said. "He honestly had no idea.

"He was 100 per cent Europe, the way he was training and everything.

"He never even saw an oval except for Phoenix before this. Impressive, really impressive."

Rossi said working with experienced Andretti team-mates Ryan Hunter-Reay, Marco Andretti, Carlos Munoz and Townsend Bell had allowed him to get to grips with oval racing quickly.

"I obviously was comfortable with it," Rossi said. "Because we have a five-car team, we were doing organised group runs at the end of every single day.

"All four other drivers were totally willing to help me understand how the car's supposed to feel, what you're supposed to do, little tricks.

"We discuss things. It's a huge effort on all of our parts. I'm just honoured to be able to drive next to all four of them."

Rossi raced for Manor in the latter part of the 2015 Formula 1 season, and has retained a reserve role with the team alongside his IndyCar commitments this year.

Asked if he was aiming for an F1 return in 2017, Rossi replied: "I can certainly say I'm not in a grand prix car anytime soon.

"I'm a reserve driver. I sit around and pretend to look important."

Andretti said he had kept an eye on Rossi's rise in Europe, which began when he won a BMW Sauber F1 test as a prize for triumphing in Formula BMW's World Finals in 2008.

"We followed his career all the way through," said Andretti.

"He was our hot, young American prospect to be in Formula 1. He finally achieved his goal last year, which was awesome.

"Unfortunately it didn't work out for him. Maybe in the end, it could work out."

Rossi added: "Things didn't go quite according to plan for 2016 in Europe.

"Things worked out incredibly well for me to come here and work with Andretti Autosport with a car they were forming with Bryan Herta.

"Four months later, here we are."