Alexander Rossi ended the second practice session from Detroit on top of the timesheets, dominating proceedings in the Michigan state.
The 27-year-old, who narrowly missed out on his second Indianapolis 500 win last weekend, set a 1:15.1367 which was half a second ahead of the competition.
Josef Newgarden was second, ahead of Scott Dixon, who headed the opening practice session earlier today.
The second Penske of Will Power was fourth, leading Graham Rahal who was the last driver to fall within a second of the fastest time laid down by Rossi.
Ryan Hunter-Reay was sixth, ending the session in front of Spencer Pigot and James Hinchcliffe.
Fresh from his victory at the Indy 500, Pagenaud ended up in ninth place, but his day didn't go smoothly as he ended the session with a stoppage on track, causing a red flag.
Ed Jones rounded out the top ten, with just one-tenth of a second separating the ECR driver to Hinchcliffe's time inside the top ten.