Sometime IndyCar driver RC Enerson will make his return to the series at Mid-Ohio round, competing for Carlin in a race that was originally part of Patricio O'Ward's deal.
Enerson made three IndyCar outings with Dale Coyne Racing in 2016 and took a best finish of ninth at Watkins Glen and has since competed in Indy Lights and the IMSA SportsCar Championship sporadically.
The 22-year-old has been intermittently linked with a return to the open-wheel category since and he drove for Carlin in pre-season testing.
Enerson will now become the fourth driver to pilot the Chevrolet-engined #31 car in the 2019 season.
"It's really great to be back driving with Carlin after completing Spring Training earlier this season with the team," Enerson said.
"We've been working really hard to get something together to get me back in the seat at some point this season and I couldn't be happier that it's all come together for Mid-Ohio.
"I know we have some work to do this weekend, but I'm confident that with both my experience and the team's at Mid-Ohio we can put together a solid result."
Indy Lights champion and Red Bull Formula 1 junior O'Ward had been slated to contest the Mid-Ohio race at the start of the season.
But O'Ward has already sat out races in Toronto and Iowa and has been focussing on opportunities in Formula 2 and Super Formula after his recent induction into the Red Bull programme.
Carlin fielded Sage Karam at Toronto and Iowa but he will now vacate the cockpit for Enerson, pictured below, who will line up alongside Max Chilton.
"We're excited to have RC Enerson and the Lucas Oil School of Racing [sponsor] on-board this weekend in the No. 31 entry at Mid-Ohio," said team boss Trevor Carlin.
"RC really impressed us at Spring Training at COTA at the beginning of the season and we were very hopeful that something could come together at some point that would put him back in the car.
"RC has spent a lot of time with our team this season and he has quite a bit of experience at Mid-Ohio, including an IndyCar start a few years back, so he should be able to jump right back in and make the transition a smooth one."
Get unlimited access to the world’s best motorsport journalism with Autosport Plus