Johnson tells Danica don’t go to NASCAR part-time

FONTANA, Calif. -- Jimmie Johnson has some advice for Danica Patrick if the IndyCar star really wants to make the move to NASCAR: don't do it part-time.

Patrick has reportedly signed a three-year extension to remain in IndyCars with Andretti Green Racing, though she is in preliminary talks with JR Motorsports about dabbling in NASCAR's Nationwide Series sometime down the road.

The three-time defending Sprint Cup champion would welcome Patrick to the circuit, but he's not sure splitting time between the two series is the best way for IndyCar's most popular driver to make the transition.

"Seat time is everything," Johnson said. "You've got to learn these cars, learn these tracks. She may have raced on these tracks, but not in a closed-body vehicle."

If Patrick is serious about becoming competitive in stock cars, Johnson thinks she needs to commit to more than a handful of races a year.

"Drive everything with a body on it, ARCA, Truck, (Nationwide), Cup, hit some walls," he said. "It's going to be tough because she's obviously going to have the spotlight on her. But hit walls, tear up equipment, make mistakes, you have to go through that."

It's a process that can be a struggle for even the best open-wheel drivers.

It took Juan Pablo Montoya two full seasons to get comfortable in stock cars after leaving Formula 1. Now he's third in points heading into today's 500-mile race at Auto Club Speedway.

Montoya rarely ventures outside stock cars these days save for the Rolex 24 at Daytona shortly before the season-opening Daytona 500. Even then, he said, after just a couple days of testing and racing in the Rolex, it feels "weird" when he gets back in a Cup car. Montoya called the difference between driving open-wheel cars and stock cars "night and day."

And Montoya is one of the lucky few who have made the move successfully.

Former IndyCar champion Sam Hornish Jr. is finally making progress in his second full season driving Cup cars for Penske Racing.

Dario Franchitti spent a few ill-fated months in NASCAR in 2008 before moving back to IndyCars, and captured this year's points title.