Four-time Indianapolis 500 winner Al Unser will...

Four-time Indianapolis 500 winner Al Unser will replace critically injured Roberto Guerrero this weekend as driver for Vince Granatelli’s Indy car team in the Bosch Grand Prix.

Guerrero was unconscious and in critical but stable condition at an Indianapolis hospital after suffering head injuries in a crash during a tire testing session at the Indianapolis Motor Speedway.

Unser, who passed Guerrero late in the Indy 500 in May and went on to win the race, with the Colombian finishing second, will drive Granatelli’s March in Sunday’s race at the new Pennsylvania International Raceway.