Paul Tracy will not be racing for AJ Foyt's team at this weekend's event in Texas after splitting with the team.
The Canadian replaced the injured Vitor Meira in last weekend's race in Milwaukee, where he finished in 17th position, six laps down.
Tracy said Foyt had told him he was "embarrassed" about the car the Canadian had in that race, and reckoned it was best to split for the time being.
"I spoke with Larry Foyt yesterday to say, 'okay, let's do this season', and he appreciated that, and said he'd discuss it with his dad," Tracy told Racer.com.
"Then later, A.J. called and said, 'Look, I'm embarrassed about the car we gave you in Milwaukee. I can't afford to be putting you in my equipment until we've got ourselves up to par. Having you in the car puts our team under the microscope, and I want to get our team better before we do that again'."
He added: "A.J. is a straight-up guy. I'd never worked with him before last weekend, and I liked his attitude of trying to get things done. So I've basically told him that any time he wants to run me - and I'm talking a race or even a test - then he just has to call. I'd be really happy to help.
"I'm sad not to continue with Foyt. I was looking forward to traveling to races again and helping a little team punch big. But ultimately it's the team's decision. I hope we can work together again soon."