Mike Conway will miss the IZOD IndyCar Series finale this weekend at Auto Club Speedway, Fontana in California, after he informed his team AJ Foyt Racing that he was no longer comfortable competing on ovals.

"I've come to realize I'm not comfortable on the ovals and no longer wish to compete on them," said Conway on Thursday afternoon. "I'm truly sorry for putting the team and our sponsors in a difficult position, but this is the hardest decision I have ever made in my racing career."

The English driver was quick to point out that his decision to drop out of this weekend's race at the two-mile Fontana oval did not mean that he was quitting from racing.

"I want to stress that I am not finished racing," he said. "I would love to continue with Foyt Racing, but that's something we need to discuss in the future."

Conway apparently made the decision after struggling during test runs at Fontana, which saw him running around 20th position in the timesheets some 5mph off the leaders' times.

He suffered serious neck and back injuries as well as a broken leg in a horror accident in the 2010 Indianapolis 500 that sidelined him for the rest of that season, but he had bounced back and completed a full season with Andretti Autosports in 2011.

Conway had driven the AJ Foyt Racing car to three top ten finishes this year which included a podium finish in Toronto, and his efforts have won him solid support from the team. However, this year's Indy 500 ended in another scary crash that may have brought unhappy memories of two years ago back to the surface.

Larry Foyt, the team's general manager, said that they respected Conway for turning to them and expressing his unease with running on any further oval tracks, and that it was still possible that Conway could run future street and road courses with them next year.

"Mike's been a great asset to our team, and I'm disappointed that we can't finish out the season together," he said. "It took a lot of courage for Mike to come forward and we respect him highly for that and we certainly want to honour his decision."

Conway's seat will be taken at short notice by New Zealand's Wade Cunningham, who last drove for the team in a second entry at this year's Indianapolis 500.

Cunningham won the Indy Lights race at Fontana in 2005, his championship-winning season and the last year that either Indy Lights or IndyCar ran at the Auto Club Speedway before this weekend.

"Fortunately, Wade was available to drive for us, and we're looking forward to working with him again," said Larry Foyt.

Cunningham will get special track time on Thursday for IndyCar president of competition Beaux Barfield and technical director Kevin Blanch to observe and make sure he is race ready.

"It's in everyone's best interest that he gets comfortable on the oval," said Barfield. "We have unlimited time today, so we'll watch him closely."