CHARLOTTE, N.C.  — Blame it on JPM. He’s the one who made people think any driver with a reasonable amount of talent could jump into a stock car and succeed.

But if there’s one thing that’s become painfully obvious through the first five races, it’s that Juan Pablo Montoya is the exception and not the rule to open-wheelers moving into NASCAR. Four top-notch drivers followed him this season, and have struggled mightily in one of the five biggest surprises so far this season.

Of course, Montoya warned often last season that Patrick Carpentier, Dario Franchitti, Sam Hornish Jr. and Jacques Villeneuve were not going to have an easy time wrestling the full-bodied 3,400-pound machines. Despite his decent results, he never shied away from admitting the switch to NASCAR was the hardest transition the former Formula One star had ever made.

The others have learned the hard way just how serious Montoya was.

“I didn’t expect it to be easy by any stretch, but it’s even more difficult than I thought,” said Franchitti, Montoya’s teammate at Chip Ganassi Racing.

The attention Montoya received last season while winning rookie of the year, a Cup race and a Nationwide race made the venture look promising for anyone seeking a fresh start away from fledgling open-wheel. No one expected these newcomers to match Montoya’s success. Then again, no one expected them to struggle as much as they have, either.

Villeneuve’s venture didn’t make it past the season-opening Daytona 500. When the former F1 world champion failed to make the race, he hightailed it home to Montreal days before the event. A lack of sponsorship pushed him out of the Bill Davis Racing ride he had planned to pilot, and the team has since ceased operations on the No. 27 Toyota.

Carpentier, another Canadian who raced in both Champ Cars and the Indy Racing League, has a solid team and sponsorship but can’t make races. He’s qualified for just two of five events so far, has a best finish of 35th in Atlanta and is 46th in the points standings.

Franchitti heads to Martinsville Speedway this weekend ranked 38th in points and in danger of not making the field for the first time this season. He started the year inside the top 35, thus guaranteed a starting position, but the field resets this week and he’s now on the outside looking in and needs a strong qualifying lap to make Sunday’s race.

Through five events, he’s finished 33rd three times and his best was a 32nd in California. It could be bad news for the reigning Indianapolis 500 and IRL champion, who doesn’t have full season sponsorship yet, and missing races would certainly curtail any potential suitors.

That makes Hornish the best of the group, and he’s clinging to 35th-place in the standings. The three-time IRL champion opened the season strong with a 15th-place run in Daytona. But it’s been downhill from there, with a 25th in Atlanta his best showing since.

Hornish said this season is a building year, and that NASCAR was a natural move because he had little left to accomplish in open wheel.

“I didn’t feel (open wheel) was challenging me enough,” he said. “I knew how difficult this was going to be, and I knew I’d look back at my career and if I didn’t do this, I was going to wonder ‘Could you have made it and gotten to the point of being successful?’

“I knew it was going to be difficult, that’s why I did it.”

The other surprises this season:

2. Montoya himself

His rookie campaign raised the expectations on the Colombian, and even car owner Ganassi bought into the hype when he said this season was “Chase or bust” for his driver.

Although Ganassi later downplayed the expectations, many still believed Montoya would be a legitimate threat to win on an oval and perhaps qualify for the 12-driver Chase.

But through five races, he’s 19th in the standings and still searching for his first top 10 of the season. Even worse, the places he should have contended at — fast tracks such as California, Las Vegas and Atlanta — were not kind to him.

There’s no one doubting his skill level, which leads many to wonder if the Ganassi equipment is meeting his needs. Aside from Reed Sorenson’s strong showing in Daytona, none of the three Ganassi cars has shown the same improvement the other Dodge teams have made this season.

Montoya is not pointing fingers.

“We’re trying as hard as we can,” he said. “It’s not like I can be upset and say ‘We’re not giving 100 percent’ or ‘We’re not doing everything we can.’ I know that the entire team is doing everything in its power and all we can do is keep trying.”

3. Jimmie Johnson

The two-time defending Cup champion has never in six previous seasons put together a stretch as poor as the one he’s in the midst of.

And it’s not the actual finishing position that’s troubling about Johnson’s season. It’s that the No. 48 Chevrolet has only been up front once this season, at California, where he led 76 laps and finished second.

Sure he led a lap in Daytona, and 14 more in Bristol, but it’s because he started from the pole. That’s it in a shocking start for a team that couldn’t seem to lose for much of the past three years.

Suddenly, Johnson can’t seem to get anywhere close to a win. He was 29th in Las Vegas — where he entered the race as the three-time defending winner — and followed it with 13th and 18th place finishes in Atlanta and Bristol.

Now he heads to Martinsville, where he’s won three times in a row, searching for his first victory of the season.

It’s telling, though, that his struggles have come at a time when Hendrick Motorsports is still looking for its first victory of the season. This time last year, the team already had three wins and was in the middle of a streak that saw Hendrick cars win eight of nine races.

4. Greg Biffle

He opened 2006 as a popular pick to win a Cup championship, only to struggle through the next two seasons.

The drop-off was significant for “The Biff” after he won six races in ’05 and finished second to Tony Stewart in the Chase. He failed to make the Chase in 2006 or 2007, and wound up 13th and 14th in the standings those two years.

But Biffle has skyrocketed out of the gates this year, and heads into Martinsville second in the series standings. He’s been inside the top 10 in all but one race this year, and his lowest finish was a 15th in California.

At this pace, Biffle is on track to live up to his potential of two years ago.

5. Brian Vickers

It sure seemed as if Vickers made an awful move when he left Hendrick Motorsports to be the star driver at startup Red Bull Racing.

As his old team won 18 of 36 races last season, Vickers struggled to even make the field. He qualified for just 23 of the events and finished 38th in the final standings.

It sent him into this second season with Red Bull needing to make the first five races on speed, and Vickers more than delivered by qualifying for each of them. Then, his early runs were so strong, he went into Bristol knowing he could miss the race and still leave Tennessee locked into the top 35.

He spent time inside the top 12 in points, but his 39th-place finish in Bristol dropped him to 17th. Regardless, Vickers isn’t in danger of missing races anytime soon and the seat time and race experience will only help Red Bull continue its development.