Defending Indy 500 champion Buddy Rice will not drive in this year's race because of injury.
Rice won last year's Indy 500 from pole
The Rahal Letterman team driver hurt his back and sustained concussion in a crash in practice last Wednesday.
The 29-year-old was told on Tuesday that he would not get medical clearance for the race on 29 May.
"Physically I feel fine, but I have to trust the Speedway and IRL medical team because they are looking out for my safety," said Rice.
Rice has been told to rest and will be re-assessed in three weeks.
Rahal Letterman co-owner Bobby Rahal said the team was looking to draft in a replacement driver.