Justin Wilson grabbed his second pole position of the year - and his second in Mexico City - with a great display ahead of Sunday’s ChampCar season finale.
The Brit secured his top lap of 1:24.801 with a few minutes of the session to go, but nothing his Newman/Haas Racing rival Sebastian Bourdais did could dislodge Wilson.
Speaking after the session the RUSport driver said, "Everything came together at the right time. We made some changes before qualifying that improved the car, a lot. I could get on the power earlier, everything was flowing."
The former Formula One driver's participation had been in doubt after he broke the scaphoid bone in his right wrist during practice for the last round at Surfer's Paradise in Australia two weeks ago.
He was only cleared to race at the last minute after being assessed by Champ Car's medical delegate Dr Chris Pinderski.
Wilson said, "It made a difference to my time yesterday, because I was losing time in the Esses and through the final corner.
"Today I don't know if it cost me a tenth, two tenths or nothing at all. I feel confident I'll be able to handle 66 laps tomorrow, and go for the win. If I can't, I'll play it smart and try and get second in the championship."
Wilson needs only to finish seventh tomorrow to grab runner-up slot in the title race from new NASCAR driver AJ Allmendinger, who's not competing this weekend after being dropped by his Forsythe Championship Racing team.
Bourdais admitted to being "a little disappointed" to lose pole. "After the first run, I thought I'd be on pole," he said. "I came in and we made a change to counteract the understeer that we get here as more rubber goes down.
"However, we aren't sure why, but we still had pretty bad understeer, and together with the oil going down we came up a little short. Maybe we had a rear damper problem, I don't know."
As Will Power was one of the few drivers who failed to improve his time from Friday, the Team Australia driver was edged aside by the second Newman/Haas car of Bruno Junqueira, who was half a second off Bourdais.
Ryan Briscoe took fifth in the second RuSPORT entry and will start alongside Dan Clarke, who did a great job on his first visit to the track by taking sixth place for CTE Racing-HVM.