EJ Viso has been ruled out of this weekend's IndyCar finale at Fontana, with Andretti Autosport explaining the Venezuelan's absence as being due to an illness.
The 28-year-old is understood to have informed the team of his inability to participate late on Thursday evening.
"EJ has the flu and will not race this weekend," an Andretti spokesperson told AUTOSPORT.
"We are currently evaluating our options for the #5 car."
Indy Lights frontrunner Carlos Munoz, who finished second for the team at the Indianapolis 500 in May, is expected to fill the seat.