Mikhail Aleshin and the Schmidt Peterson Motorsports IndyCar outfit have parted ways, with the Russian set to focus solely on developing BR Engineering's World Endurance Championship LMP1 car.
Aleshin, whose best result this season was a sixth-place finish in Detroit, arrived late for June's Road America race owing to visa issues after his participation in the Le Mans 24 Hours.
He crashed out of the following Iowa round and was then dropped in favour of Sebastian Saavedra for last month's Toronto race.
He returned to the cockpit at Mid-Ohio, finishing the race in 14th.
Aleshin was involved in the initial testing of BR's 2018 WEC challenger, which will be run by SMP Racing, and has remained central the development of the BR1.
"Mikhail Aleshin, the Russian SMP Racing programme driver, will not be returning to the #7 Honda for the remainder of the 2017 Verizon IndyCar Series season," read an official statement from Schmidt Peterson.
"Schmidt Peterson Motorsports and SMP Racing have mutually agreed that the Russian driver will focus on the design and development of the new BR1 LMP1 car.
"Aleshin is the key SMP Racing driver working on the new LMP1 prototype BR1 which shall be ready for its first test session in the near future.
"Designed by Russian company BR Engineering, in cooperation with Dallara, the BR1 of SMP Racing team will debut in the World Endurance Championship in 2018."
Saavedra is regarded as one of the favourites to fill in again for next weekend's Pocono round, although the team is yet to issue any update on who will drive the car for the rest of the races this season.
Veteran Oriol Servia, who has driven the Schmidt Peterson-run Honda-powered 2018 Indycar during its testing phase, is also considered an option.
Aleshin had his most successful IndyCar event at Pocono in 2016 where he scored pole position, and finished second to Will Power.