DETROIT (AP) -- Helio Castroneves surely had another fence-climbing celebration running through his mind as he raced toward victory Sunday at the Detroit Indy Grand Prix.
Then came a caution flag that cut his lead over rookie Justin Wilson to less than a second.
With Wilson breathing down his neck, Castroneves moved his race car into Wilson's path three times on lap 72, forcing IndyCar Series officials to make the rare and controversial decision to compel Castroneves to allow Wilson to speed ahead of him into first place.
Wilson held the lead the rest of the way, taking his first-ever IndyCar Series victory and sending Castroneves into a tizzy.
"I'm very surprised -- very much surprised about this call," he fumed.
Wilson had an altogether different take on the decision to penalize the flamboyant Brazilian.
"In my mind, it was so clear and so obvious that something had to be done," he said.
Castroneves led for the majority of the road race on the Belle Isle course, holding the top spot for 53 of the 87 laps.
Series points leader Scott Dixon finished fifth. That result, coupled with Castroneves' strong showing, means the IndyCar championship will be decided at next weekend's final points race at the Chicagoland track.
The odds of winning the series title still favor Dixon, who entered the Detroit race 43 points ahead of Castroneves. Dixon needs to finish eighth or better next week to win his second title and first since his rookie year of 2003.
Dixon's lead now stands at 30 points.
Wilson, an Englishman who started in the race's fourth position and drives the No. 02 car for actor Paul Newman and his Newman/Haas/Lanigan Racing team, had six top-10 finishes entering Sunday's race, including a season-best third-place run at Edmonton.
He started the day in 16th place in the series standings.
Newman/Haas/Lanigan's other victory of the season came with Graham Rahal in April in St. Petersburg, Fla.
"This is the most important win of my career," Wilson said. "It's been a long, difficult year. A lot of things have happened. A lot of things are going on, but we managed to pull through. This one means a lot, and this one is also for you, Paul."
Castroneves dominated much of race and looked as if he was headed to another win after finishing first in California last weekend, but IndyCar officials ordered Wilson's car to the lead after the blocking call was made by Brian Barnhart, IndyCar Series president of competition and operations.
"We did what we did because it was a pretty easy call," Barnhart said. "He had a tremendous run out of Turn 12, and Helio crossed over almost the entire width of the track to impede the progress of the car behind him."
The explanation did little to change the mind of Castroneves, who questioned whether Barnhart's decision was personal and why no warning was given first.
When his crew relayed the decision to him over the radio, Castroneves asked whether anything could be done, and he was told the decision would not be changed.
"It was just an unusual call," he said.
Wilson relayed a different message to his crew when Castroneves kept getting in his way.
"It was pretty severe," Wilson said of the series of blocking maneuvers. "I was upset and even complained on the radio."
The scheduled 90-lap race ended after 87 laps when the race hit the 2-hour time limit.
Tony Kanaan, last year's winner at Detroit, finished third. Oriol Servia was fourth.
Dixon, the fastest qualifier, and second place-starter Castroneves remained in first and second place for the first 18 laps, then Dixon pitted on No. 19, allowing Castroneves to take the lead position.
Dixon never regained the lead.
"That was pretty much the race," Dixon said.
On the 17th lap, Dan Wheldon made contact with rookie driver Jaime Camara. Wheldon spun into a tire barrier, but was able to restart.
Wheldon also had trouble with about 20 laps to go when he missed a turn and slowly ran into the barrier. He finished 20th and yielded third place in the series standings to Kanaan.
Castroneves didn't initially pit until lap No. 32, but only briefly and didn't lose the top spot.
Danica Patrick and Vitor Meira slapped tires a third of the way through the race, forcing Patrick's car to stall and Meira's No. 4 to head off the course. Meira, who started the race in 14th place, had to do the equivalent of a three-point turn before heading to pit road.
Patrick ended up 16th after starting 10th.