AVONDALE, Ariz. -- It's no surprise that driving a stock car is harder than it looks, but why is that the case?

Less than 40 years ago, open-wheel stars like A.J. Foyt, Mario Andretti, Dan Gurney and Parnelli Jones were just as successful in limited NASCAR racing, and stock-car aces like Bobby Jones, Cale Yarborough and Bobby Allison had competitive rides in the Indianapolis 500.

Wide open

For the first time in NASCAR, three former Indianapoilis 500 winners will be in the same Cup race including Sam Hornish Jr., who will make his first start after six failed attempts.

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So what happened?

As open-wheel cars became more dependent on downforce to increase speeds, engineering drove the technology of the sport. The skill set needed to pilot those rear-engine missiles then changed, accoring to many of the drivers entered in Sunday's Checker Auto Parts 500 at Phoenix International Speedway.

And now that many of those drivers, including three-time Indy Racing League champion Sam Hornish Jr., have followed Juan Montoya into NASCAR, the question remains: How successful will they be in making the transition?

Jacques Villeneuve understands what Hornish is going through, because he's on the same learning curve.

"The car moves around a lot," Villeneue said. "You can't drive them too aggressively. When you do, you start sliding and you lose speed. It's not that you go off, you just start going a little bit slower and slower, and that makes it difficult to set the car up as well.

"Also, the track changes all the time. So it's just getting used to knowing how much sideways you want to be for it to be fast. You think, 'Well, I'm a little bit sideways, but is it too much? Is it not enough?' That's all the kind of stuff that you just don't know because it doesn't come naturally for us."

Dario Franchitti, fresh off an Indy 500 win and IRL championship, said it's a matter of "unlearning" how to drive.

"It's the same difficulties I'm facing, just getting rid of the habits from driving an Indy car and all of the feelings you're used to in an Indy car," Franchitti said. "You have to get used to what it requires to set up a stock car and the driving style you need to make a stock car go fast, because it's quite different."

J.J. Yeley came up through the open-wheel ladder and raced at Indy in 1998, finishing ninth despite spinning out on the first lap of the race. He said Hornish will have to learn how to describe to his crew chief what his car is doing rather than rely on data downloaded onto computers.

"I think once he gets the hang of it, he'll get out there and he'll be fine," said Yeley, himself excited about his move to Hall of Fame Racing and Toyota in 2008. "It's just a total different technical package for him.

"He's used to coming in and working with an engineer and really going to it. Now he's got to go by the seat of his pants, express what he's feeling and hope that the communication is conveyed. That's the toughest part for any driver when you make it to stock cars ... the driver is a lot bigger part of what it takes to go fast because he has to tell the crew chief what he's feeling."

For Kasey Kahne, the transition to stock cars was easier because sprint cars require emphasis on car control. His biggest issue was getting used to marathon races.

"It's such a different deal. These guys have so much experience at high speeds," Kahne said. "I had no high-speed experience when I came in. I just had a lot of pavement and dirt experience, sliding around.

"I know for me, it was being able to run a full race and not make mistakes, not do things like I was racing a 30-lap race. Me, just slowing down a little bit helped. [Hornish] will figure it out, the driving part."

In Jeff Gordon's opinion, Hornish may be too set in his ways to make a successful transition.

"I am a little surprised that he hasn't run a little bit better, at least made the races," Gordon said. "I have always been a big fan of Sam's. I have always felt he is a very talented driver.

"I think the biggest thing that is hurting him right now is that he has been in those cars a little bit too long. The longer you are in a car like that, the longer it is going to take you to transfer over to this kind of car."

Kurt Busch will be teammates with Hornish in 2008, and will get a firsthand view of Hornish's transition.

"It's yet to be determined what will happen and how it will play out," Busch said. "Sam Hornish Jr. has accomplished quite a bit in his IRL career as a three-time champion and to have as many race wins and of course an Indy 500 crown.

"He's done incredible things and so we hope he's able to bring that success over to the stock car level, but this stock car thing is pretty tough. I don't think it should be taken for granted that this is easy to do even though we are having an onslaught of open-wheel drivers heading our way."

Still, when all is said and done, talented drivers learn to adapt. Busch is betting that once he learns the tracks and adjusts his driving style to the car, Hornish will catch on.

"What was odd to me is he had never been to Dover, he had never been to New Hampshire and he had never been to Charlotte," Busch said. "I started scratching my head. I thought the IRL had raced at Charlotte and Dover and New Hampshire, which they have, but they raced there a couple years before Sam had gotten there.

"So it's amazing to me that he's cranked out three championships over there right away and what that leads me to believe is that he is quick to adapt, that he'll have the right approach and so it'll be a team discussion on who's going to help whom out. It sounds like if he gets on it, he'll make these races and he'll be a threat."