Raffaele Marciello will move to Russian Time for a third GP2 Series season in 2016, but has lost his Sauber Formula 1 third-driver role.
The announcement of Marciello's new GP2 deal also made no reference to Ferrari, which has supported his career via its Driver Academy since he graduated from karting at the start of 2010, amid reports that he is no longer part of the Scuderia's junior programme.
The 21-year-old Italian won the 2013 European Formula 3 title, before beginning a GP2 career that has so far only brought one race win - at Spa in his rookie year with Racing Engineering.
Marciello was seventh in the points with Trident last season, when he dovetailed GP2 with Ferrari F1 test duties and a Sauber drive that included four appearances in grand prix Friday practice sessions.
A Sauber spokesperson confirmed to Autosport that its deal with Marciello had expired and would not be renewed.
Marciello has still secured a third season in GP2, switching to Russian Time to become team-mate to Artem Markelov.
Svetlana Strelnikova's squad won the teams' title at the first attempt in 2013 after taking over the iSport operation, with lead driver Sam Bird only narrowly missing out on the championship in the same season.
Mitch Evans has continued Russian Time's race-winning form for the past two years.
Strelnikova believes an experienced line-up is the right choice to keep Russian Time among the frontrunners in 2016.
"[Marciello] has shown consistent speed and Artem has grown stronger as he got to grips with the category," she said.
"I'm optimistic that with both drivers having two years' experience in F1's feeder formula, we will be able to mount a challenge in what is an ever more competitive series."
Evans has been linked to a move to Campos Racing for what would be a fourth season in GP2 for the 2012 GP3 champion.