MARTINSVILLE, Va. -- Now it's time for some real investigation by NASCAR.

What the heck is going on with Jimmie Johnson's slump? Perhaps taking his No. 48 Chevrolet back to NASCAR's Research & Development Center for a complete teardown is in order now like never before -- and it's been going back to the R&D Center pretty much on a weekly basis for some time now.

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Jimmie Johnson says he had a second-place car all day and didn't think he had anything for winner Denny Hamlin.

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But get this: Johnson didn't win Sunday's Tums Fast Relief 500 at Martinsville Speedway. He finished second to race winner Denny Hamlin.

That's the lowest Johnson has finished in the past three races during the Chase to the Sprint Cup. And therein lies the problem for the competitors pursuing Johnson in the Chase: Even on a day when he "struggles" to some degree, he's still better than most.

That was the case Sunday, when Hamlin was the only Chaser to gain points on the three-time defending champion. And after gaining a total of 20 by virtue of the victory, Hamlin, who moved up two spots to ninth in the standings, still trails Johnson by an obviously insurmountable 352 points with only four races left in the season.

Everyone else fell farther behind Johnson in the standings by virtue of Sunday's results. His two Hendrick Motorsports teammates who also happen to be the two drivers closest to him in points now head into next Sunday's race at Talladega behind by more than 100 points -- with Mark Martin in second trailing by 118, and Jeff Gordon in third down by 150.

"For them all to have one less race to gain points on us is huge," Johnson admitted. "We opened up a few points on those guys who were closest to us in the standings. So mission accomplished. One more race down on the 5 [Martin] and the 24 [Gordon], and four to go."

Johnson insisted -- again -- that he will not rest easy until his unprecedented fourth consecutive championship becomes official, until all others are mathematically eliminated. Plus he knows the chaotic nature of races at Talladega, where anything can and usually does happen.

"I've been trying to forget about Talladega," Johnson admitted. "I have no idea what we can do there to avoid problems. It's like being in Vegas. It's a crap shoot.

"You can't relax until it's mathematically over. I know I would feel really good and really positive about things if we get through Talladega, because the rest of the tracks are usually really good for us. But you could have a flat tire or something else happen. ... If something like that happens to you, what can you do?"

Well, you can cruise to another championship anyway. Johnson has that kind of cushion and there is little time and opportunity left for the others to make up ground on him.

It's not like the rest of the Chase field struggled -- by their standards -- at Martinsville. Juan Montoya finished third in the race, right behind Johnson, to move up to fifth in points while nonetheless dropping another five points off Johnson's pace to bring his deficit total to an even 200. Gordon finished fifth in the race, while Martin was eighth.

Other Chasers who finished in the top 10 at Martinsville included Stewart-Haas Racing teammates Ryan Newman (seventh in the race and the standings, 312 points behind) and Tony Stewart (ninth in the race and fourth in the standings, 192 behind).

Asked what someone has to do to possibly catch Johnson, Montoya replied: "The way he's running, you've probably got to win the next five races and he's got to have some bad luck."

Problem is, there are only four races left. And Johnson seems to make his own luck of the other kind.

The weekend at Martinsville was different than others he has experienced lately, as nothing seemed to come easily. He was coming off what he and crew chief Chad Knaus called the "perfect" race weekend in Charlotte when he won the pole and the race and posted the fastest lap times in every practice in between.

At Martinsville, he was only 15th-fastest in qualifying, ninth-fastest in the only practice session because the rest were rained out, and chased Hamlin and Montoya around the .526-mile short track much of Sunday afternoon.

"You don't have weekends like last weekend very often," said Johnson, who still led 164 laps Sunday, second only to Hamlin's race-high 206. "I mean, I'm eight years into doing this and it was the first time we experienced that. I knew this track was going to be tough. I knew at the end, the 11 [Hamlin] and the 24 were going to be tough to beat. I think Juan did a hell of a job figuring this place out. I didn't anticipate him being that strong, but he was.

"You can't take anything for granted. I keep saying that and it's hard to believe me after we win a race or two. But you've got to just keep fighting for every position. These guys are all good at what they do, and it's tough to battle with them every week."