Dan Wheldon Gave Someone The Finger Before Winning 2011 Indy 500

With about 15 laps to go in the 2011 Indy 500, Dan Wheldon was running hard to make up ground on the leaders. But after getting in dirty air, Wheldon lost momentum and allowed an unnamed driver to pass him. That driver needlessly pushed Wheldon toward the wall and the eventual winner voiced his displeasure as he repassed him.
From Wheldon's appearance on the Opie and Anthony Show in June 2011

[@Alex_Mac_]

Who could the driver on the receiving end been?