SONOMA, Calif. - Jimmie Johnson and teammate Jeff Gordon had an unexpected and unwanted day off Friday.

The cars of defending NASCAR Nextel Cup champion Johnson and series points leader Gordon failed inspection and were barred from all activity for the day at Infineon Raceway, including qualifying.

NASCAR said the No. 24 and No. 48 Chevrolets, both owned by Hendrick Motorsports, had modifications to the front fenders that were deemed illegal during morning inspection.

The Hendrick crews were allowed to repair them and they can race in Sunday's Toyota/Save Mart 350, although starting from the rear of the 43-car field. Gordon, the four-time series champion, is the defending race winner.

“The cars have been repaired and I'm under the impression they will not receive an inspection sticker until tomorrow morning, which will allow the cars onto the racetrack,” said Chad Knaus, Johnson's crew chief. “The guys on both teams have done a good job getting the cars repaired. They are race-ready now.”

But the damage was already done.

Doug Duchardt, vice president of development for Hendrick, called the modifications an honest mistake.

“We've been evolving and this was just the latest evolution of what we've been doing,” he said. “Our understanding is that our cars fit the templates but that they were outside of what they would like to see within the templates.”

Gordon came to Sonoma after his wife gave birth to the couple's first child, a daughter, on Wednesday.

“Well, obviously, nothing's going to ruin my day or weekend,” Gordon said. “I'm on cloud nine. This has obviously been pretty devastating news at the race track. ... This definitely puts us in a box and we're going to have to work our way out of it.”

The five-time Sonoma winner said pit strategy is going to be “extremely important.”

“We're one of the best teams out there,” he said. “I love the road courses and I know these guys have brought a great race car and I'm looking forward to getting out there, hopefully sometime tomorrow, and seeing what we've got for them on Sunday.

Johnson echoed his teammate and the co-owner of his car.

“We're going to start at the back and work our way forward,” he said. “A lot of road course racing really falls into the strategy of the race and we'll just have to make the most of our poor track position to find the strategy and work our way up for a solid finish.”

This is the first road race for NASCAR's new Car of Tomorrow, a bigger, bulkier and reputedly safer car that's been in development for seven years. It has run in six races this season, all on ovals.

“It's important to know that this is a Car of Tomorrow penalty,” NASCAR spokesman Ramsey Poston said. “The inspection process and NASCAR's reaction to the Car of Tomorrow violations are going to be more severe. We're going to keep this car in check.

“It's important to know that all cars in the field are starting out equal and all have the same opportunity to win as the other.”

Dale Earnhardt Jr. was docked 100 points and crew chief Tony Eury Jr. was fined $100,000 and suspended six races after NASCAR discovered illegal brackets on the rear wing of the No. 8 COT Chevrolet last month at Darlington Raceway.

Last year, Knaus, was suspended for four races when he was caught cheating in qualifying before the Daytona 500. Johnson won the race without Knaus, who rejoined the team in March and helped Johnson win the Nextel Cup title.

Asked why the cars could still be allowed to pass inspection and race this weekend, Poston said: “That's been our practice in the past that we've given teams an opportunity to repair cars that have failed inspection, and we'll do the same here.”

Poston said NASCAR would determine any further penalties assessed to the two Hendrick cars after officials return to their Daytona Beach, Fla., headquarters following the race.

Kurt Busch, who drives for Penske Racing, said he understands what NASCAR is trying to accomplish with the COT.

“If NASCAR's intentions are to create an equal playing field for everybody with the COT and you step out of line like this, you need to have your hands smacked, I guess,” Busch said. “DEI did it with their rear spoiler and now you've got two Hendrick cars that are out of code.”

But Busch said he doesn't expect missing a day of on-track action to slow down the Hendrick cars.

“You lose a little bit of practice time, but it's only an hour and a half today,” he said. “It's not much. It's going to be bad though with those two cars starting in the back because guys up front aren't going to get any TV time.”

Duchardt noted his team has won five of the first six COT races and each of those winning cars was sent to NASCAR's Research and Development Center and encountered no problems.

Hendrick has won 10 of 15 races overall this season, with both Gordon and Johnson winning four times. Their teammates, Kyle Busch and Casey Mears, whose cars passed the initial inspection Friday, have each won once.