The driver Cup fans love to hate has been the scourge of the stock car sport this season, winning a series-high eight races during the "regular season" in Cup, adding seven more wins in the second-tier Nationwide Series and three in the truck circuit.
The 23-year-old wunderkind had led the Cup standings since the 10th race.
All of that added up to the expectation that Busch would be the guy to beat for this year's championship.
But a broken part in his No. 18 Joe Gibbs Racing Toyota turned Sunday's Sylvania 300 at New Hampshire Motor Speedway into a near-disaster for Busch, who was so upset he left the track without speaking to the media.
It was only thanks to some late attrition in the race that Busch didn't wind up worse than his 34th-place finish in the 43-car field. He fell to eighth in the standings, 74 points behind co-leaders Carl Edwards and Jimmie Johnson.
For the start of the 10-race Chase, the 12 eligible drivers were seeded by wins, with a 10-point bonus for each victory. The hopeful Busch began the day 30 points ahead of Edwards, 40 in front of two-time reigning Cup champion Johnson and 80 ahead of the four Chase drivers who have not won this year.
Everything seemed to be going his way this week, too, when despite struggling with an ill-handling car in practice, qualifying was rained out and the drivers were lined up by points -- putting Busch on the pole.
But it was obvious from moments after the green flag waved Sunday that something was wrong.
After leading the first three laps of the race, Busch slid back through the field and smoke curled from the rear of his car as he drove through the turns. On lap 20, the rear end swung out and clipped the wall as he drove through turn two on the 1.058-mile oval.
Busch continued, but things just got worse after that.
The radio chatter between Busch and his pit began referring to the possibility of a broken sway bar and, on his first pit stop, those fears were confirmed: a broken bolt on the front sway bar was allowing the rear of the car to slide dangerously in the turns.
Busch, penalized for passing the pace car to get into the pits on that first stop, was held on pit road for a lap.
He and new crew chief Steve Addington still had hopes of getting the problem corrected and making up that lost lap until Busch spun on lap 83. He missed the wall, but as Busch slid through the infield grass back onto the track, Jamie McMurray collided with David Ragan and banged hard into the rear of Busch's car, doing considerable damage.
Again Busch continued but, this time, he came out of the pits eight laps behind the leaders and was so slow that he was lapped four more times before the end of the race.
"We had a part failure and it's one of those things you can't do nothing about," Addington said. "We weren't very good when we unloaded here, but we felt like we did the right things and were going to have a good race car. (That) part failure cost us, so we'll just have to go back and re-evaluate."
Two-time Cup champion Tony Stewart, who had his own problems in finishing eighth on Sunday, had some advice for his Gibbs' teammate.
"He just needs to go home and forget about it for the week," Stewart said. "He's been the dominant force all year and today was one of those odd days for him. You feel bad for him because you know they're better than that.
"But, you know if there's anybody that can rebound from a day like today, it's that 18 car. ... They're not out of this, yet."
History does show Busch still has a legitimate shot at the title with nine races to go.
In 2006, Johnson got off to a miserable start in the Chase, finishing 39th here and falling to ninth in the points. He followed with finishes of 13th, 14th and 24th before getting rolling. The next five races, Johnson finished second four times and won the other, then wrapped up his first title with a ninth-place finish in the finale at Homestead-Miami Speedway.
On the other hand, 2004 champion Kurt Busch, Kyle's older brother, won at New Hampshire, 2005 champion Stewart began the Chase with a runner-up finish, and Johnson started his second title run a year ago with a sixth-place finish. All were either first or second in the points leaving Loudon.
"When I was in that position, we couldn't do much about it," Johnson said, talking about his bad start in the Chase two years ago. "It is what it is. We just really went on and fought through the rest of the season.
"Luckily, things came our way. So, at this point, Kyle's hoping everybody has a bad race. I just think it's way too early in the Chase to count anybody out. We just have no clue what's going to happen in the races to come."
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