The 34-year-old Rahal Letterman Lanigan Racing driver started on a set of softer alternate tyres and jumped out to lead the opening 21 tours of the 110-lap contest as he sought a first win since Detroit 2017.
Rahal pitted on lap 22, pushing one lap farther than any other driver that began on the same tyre strategy, but was plagued by traffic during his out-lap and fell to fourth once the field cycled through their stops.
From there, it became a slow decline down the running order, which accelerated following a fuelling issue on his final pitstop on lap 81, dropping him from eighth to 12th. Rahal then lost another spot when Race Control held the yellow flag for several seconds after Agustin Canapino (Juncos Hollinger Racing) was stalled off course on lap 83.
The caution finally came out the following lap but the damage was done as Rahal was stuck in 13th, moving up one position late on following a late spin by Colton Herta to finish 12th.
No driver that started the race on alternates finished in the top five.
“Wrong place, wrong time a lot,” said Rahal, who had taken a second pole position of the season in qualifying. “Every time we came out of the pits, we were in a gaggle of cars.
“Every time we came into the pits, we had lapped cars in front of us. That cost us a lot of time.
“The Canapino deal cost me four or five seconds on an in lap, which cost me three or four spots three spots.
Source: Autosport