Conor Daly has been called up to replace Rocky Moran Jr in the #18 Dale Coyne Racing entry at Long Beach this weekend, a day after Moran joined the team.
Moran - who was announced as a last-minute replacement for Carlos Huertas on Friday - was ruled out after suffering a broken thumb in an accident with Carlos Munoz during yesterday's second practice session.
"It's a shame to see Rocky break his [thumb] like he did, but this is why I bring my stuff to the track every week, and this is why I'm here, and this is why I'm ready," Daly said.
"I can't thank Dale enough for the call, to be able to get out there and so some laps and get in the game.
"We'll see what happens, but I'm excited for the opportunity."
Daly's only previous IndyCar appearance was at the Indy 500 in 2013, when he finished 22nd in an AJ Foyt entry.
He tested for Schmidt Peterson during the off-season, and said that he is keeping his expectations in check for this weekend.
"We're not here to set the world on fire," he said. "We're here to learn.
"At least I've been on the track this weekend [as driver of the two-seater].
"I've always wanted to race [an IndyCar] on a street course, and especially here at Long Beach."