HOUSTON -- IndyCar and Helio Castroneves return to the scene of last year's heartbreak, the temporary street circuit where Dario Franchitti's career ended with a vicious crash and Castroneves saw yet another series championship slip away.

Franchitti, a four-time series champion and three-time Indianapolis 500 winner, was completing the last lap of a doubleheader event at Reliant Park when he came upon the slower car of Takuma Sato in Turn 5. That section of the circuit is one of the fastest sections of any IndyCar venue, and Franchitti had precious little time to react.

The contact with Sato's left rear tire launched Franchitti into a fence that couldn't hold the incredible force. As Franchitti's car exploded in thousands of pieces, debris scattered into the adjacent grandstand. It was an ugly scene with consequences.

About a dozen spectators were injured, most suffering cuts and bruises. Franchitti broke his ankle and his back, but it was the trauma to his head that led neurosurgeons to recommend he retire from the sport he so much loves.

Franchitti, then 40, announced his retirement a month later at the Indianapolis race shop of his boss, Chip Ganassi. He was replaced in the No. 10 car by 2013 Indianapolis 500 winner Tony Kanaan, who will compete this weekend.

Castroneves, who drives for Team Penske, entered last year's doubleheader 49 points ahead of Scott Dixon in pursuit of his first IndyCar championship. With only three races left, it seemed like a safe lead for the Brazilian. But it wasn't.

A shifting issue caused by a crew error in the Saturday race caused the car to spend nine laps on pit road for repairs early in the race. Castroneves had been the only driver to complete all 2,003 laps to that point in the season. He finished 18th of 24 drivers, and the combination of Dixon's victory and his mechanical trouble knocked 41 points off his series lead.

"To have that kind of scenario was very frustrating, but there was nothing we could do," Castroneves said this week. "Now, for sure, we learned our lesson."

Things got worse for Castroneves on Sunday. His car bottomed out on a rough stretch of the front straightaway, breaking the gearbox. He finished 23rd. Dixon finished second to Will Power to complete a total upheaval of the standings. Castroneves had come to Houston 49 points ahead, and he left 25 points behind.

Dixon won the championship -- his third such title -- two weeks later at Auto Club Speedway in Fontana, Calif. Castroneves finished second for the third time in his career.

This year, Castroneves enters the event in second place, trailing Power, his teammate, by 39 points. That's not much given that the season will reach its halfway point after Saturday's race, and there are still two oval races that will award double points. One of them is July 6 at Pocono Raceway.

Combining the Houston and Pocono races, one driver could earn up to 209 points.

"Man, the guy who does well in the next two weeks can be easily set for the end of the year," Castroneves said.

As for this racetrack, key portions of the 10-turn, 1.6-mile circuit have been repaved to reduce bumping, and the fencing where Franchitti has been fortified. The grandstand that held the injured spectators has been relocated.