Rahal was team-mates with Justin Wilson, who lost his life in an IndyCar crash at Pocono in 2015, at Newman/Haas Racing for the 2008 season following the unification of series.
In the aftermath of Justin’s death, Rahal went to huge lengths to organise a charity auction on eBay to benefit his wife and daughters.
Following Stefan’s crash in practice at Indianapolis on Monday, in which he suffered a fractured vertebra that ruled him out of the race after qualifying 25th, Rahal received a call from Wilson’s team boss Dennis Reinbold.
Rahal was also team-mates with Justin at Dreyer and Reinbold for one race at Iowa in 2010, and that helped steer his decision to step into Stefan’s #24 Cusick Motorsports entry on Sunday.
“In some other situations, I don't think that it would have excited me as much,” said Rahal.
“But being that it was Stef, and being that it was a Wilson, and in the situation that it was in, I just felt like it was my calling to jump in and help.
“I don't feel good about filling in for an injured driver. I feel for Stefan. It's a very unfortunate situation.
“When I saw the accident, I was very concerned for his back right away, when I saw the angle of the accident and, unfortunately, I'm aware of those things because of being a taller driver. It is an issue we I feel like have a little more frequently.”
Rahal paid tribute to the Wilson family in his press conference on Tuesday, and said Justin was a key part in shaping his career right from his junior category days in America.
“The Wilson family, certainly in my life, has had a very strong impact,” he said. “As I said [after being bumped from the field in qualifying on Sunday], everything in life happens for a reason. Sometimes it doesn't make a whole lot of sense.
“I think about Justin a lot. When the call came, right away it was an immediate connection. Frankly, I think in many ways, Justin helped – in more ways than one – to kind of shape my career.
“Not only as a man and who you should be, how you should act, all that stuff, but also I remember in 2006, when I was in Formula Atlantic. We had a joint autograph session with the Champ Car guys in Portland. I was still dreaming that hey, maybe [I’d race] someday Formula 1, and Justin Wilson was the guy who told me that it was way too political and I didn't have the right filter to enter F1.
“If it were not for him, I probably would have kept chasing a different dream. In many ways, he did help me, but I do know as a team-mate, too, when I was with him at Newman/Haas and then again with Dennis at Iowa, he was just a tremendous, tremendous guy, and Stef is right there with him.
“Their entire family I have the utmost respect for, and in a scenario like this, I felt had it been something different, I don't know how compelled I would have been, particularly with the storylines of the last couple days.”
IndyCar has announced a special practice session on Thursday for both Rahal and Katherine Legge (Rahal Letterman Lanigan Racing), the other driver who was involved in Wilson’s crash. The 15-minute session will take place from 4:30-4:45pm local time.
Each team will be allowed unlimited install laps within the time frame. They will not be allowed to stay on the track to cross the start-finish line and the Yard of Bricks.
