CHARLOTTE, N.C. | Juan Pablo Montoya never meant for his move from Formula One to NASCAR to be the one that made devout open-wheelers accepting of stock cars. But in the 15 months since he made the switch, the list of followers has grown.

Now Montoya has a warning for those considering NASCAR: It's a lot harder than it looks.

"This is not easy," Montoya said. "I think the person who thinks that it is easy should look again, because I think this is pretty hard. And now, with the full fields, even getting into the race is very, very hard."

Montoya has paid attention to the plight of Sam Hornish, who is debating whether or not to leave the IndyCar Series for NASCAR. A three-time series champion and Indianapolis 500 winner, Hornish has accomplished everything he set out to do in open-wheel and is craving a new challenge.

But he's gotten more than he ever bargained for in NASCAR, which has been nothing short of an incredible struggle.

Hornish has failed to qualify for the four Nextel Cup races he's entered, and has been just OK in eight Busch Series races, with a 15th-place finish at Atlanta earlier this season his best showing. Montoya said he watched Hornish's qualifying lap at Lowe's Motor Speedway last week, and instantly recognized that Hornish has yet to adapt to differences in the cars.

"When Sam went into Turn 1, I knew right then he wasn't going to make the race," Montoya said. "He never arced the corner. He was just like an open-wheeler and went straight to the bottom, and he just came out going high out of the corner. With these cars, you have to arc them and work a little more."

Since Montoya's move to NASCAR last summer, drivers have watched his progress and flirted with the series. Hornish joined him in Busch races at the end of last season, and hopes to decide soon if he'll race full-time in the Nextel Cup Series next year.

Already signed up for a full Cup schedule is former Formula One world champion Jacques Villeneuve and reigning IndyCar champion Dario Franchitti, who will be Montoya's teammate at Chip Ganassi Racing. Scott Speed, who spent almost two years in F1 before he lost his ride this summer, plans to run a full ARCA schedule next year to prepare for NASCAR.

But for now, Montoya is curious to see what Hornish will do.

"Right now, I would think he's thinking about bailing (on NASCAR)," Montoya said. "But he's just got to be patient. I asked him why he wasn't running Busch, and he said his team doesn't have enough people. If they want him next year here, he should be running as many races as he can right now. He needs seat time and he needs miles."