Maybe it's the fact that he's going to become a first-time father this summer. Or maybe it's because he has already accomplished something that no one in the history of NASCAR has ever done -- winning four straight titles -- yet he still gets asked if he's more lucky than good.
Or maybe he's just tired of being questioned every week about whether his domination and perceived vanilla personality are bad for the sport.
Whatever the reason, this much is certain through the first three races of the 2010 Sprint Cup season: There is a newfound edginess to Jimmie Johnson this year.
You saw it -- and heard it -- in Las Vegas on Sunday at the Shelby American 500. During most races, Johnson is relatively quiet over the radio, letting crew chief Chad Knaus and his spotter do most of the talking. He excels at succinctly articulating what he's sensing in the car to Knaus. From where I sit, this is Johnson's defining skill and the biggest reason why he's the best driver of his generation.
But this wasn't the case during Sunday's 400 mile event. Johnson was more verbose than usual and throughout the race there was a different tone in his voice -- more serious, more stern, more urgent -- as he challenged his crew to be fast on pit road and to improve the handling of his car. It was a little thing, but to me, it revealed a lot.
For Johnson, the stakes were raised on Sunday for one reason: he doesn't like being called lucky, which is what Kevin Harvick called him last week after Johnson took the checkered flag at Fontana. He's also grown weary of being labeled as corporate, boring, vanilla and bland. Almost every week, another story is written in some newspaper or website that harps on Johnson's supposed lack of personality. He will be the first to tell you that this has been going on for about five years. The reigning champ rarely shows anger when the cameras are on, but talk to him about this in private, and his annoyance becomes clear.
"I don't get it, the whole lack of personality thing," Johnson told me back in January as he sat in his office at Hendrick Motorsports in Concord, N.C. "It's a story that will never die. I try to show people the real side of me and let people into my life, but it's never good enough ... I just don't get it."
I really don't either. I wrote an SI cover story on Johnson two years ago that detailed why, I thought, his biography was as compelling as any driver's on the circuit. Consider his unlikely rise:
He spent time growing up in a trailer park in southern California. His mother drove a school bus. He nearly died in the Baja 1000 several years ago after crashing in an isolated spot in the desert. He was a middling driver in the Nationwide Series when, seemingly out of nowhere, Jeff Gordon and Rick Hendrick offered him the chance of a lifetime and handed him the keys to the No. 48 Chevy; and he single-handedly convinced skeptical bigwigs at Lowe's during a face-to-face meeting to take a chance and sponsor his car.
And, oh yes: he's married to model, owns a jet, lives in a mansion, has a killer apartment in the Chelsea section of Manhattan, and hobnobs with more celebrities and sport stars than any other driver in NASCAR.
Has Johnson experienced luck in his racing career? Absolutely. The fact that he drives for the biggest team in NASCAR and has the best crew chief in the sport certainly helps him win races. But Johnson has been dominating the sport for four years now.
"If people are trying to find a way not to accept the quality of the race team we have, that's cool," Johnson said Sunday. "We'll just come back next week and take the trophy again."
Three weeks into the season, Johnson and Knaus have already won two races. The dynasty rolls on. On Sunday, Johnson became NASCAR's all-time winningest driver on 1.5-mile tracks with 15 victories (Dale Earnhardt Sr., Jeff Gordon and Richard Petty have 14) and in the coming weeks and months more records surely will fall.
As Johnson talked to the media late Sunday afternoon in the press center at Las Vegas Motor Speedway, there was an air of defiance to him. If his body language could talk, it would have said, "Screw you if you think I'm boring and lucky."
Will Johnson be hoisting the big trophy at season's end once again? It's still way too early to tell, but we already know this:
An edgy Jimmie Johnson is a fast Jimmie Johnson.