But with news of the related Russian rescue deal having gone silent, it surprised some observers this week when Sauber said the McGregor-sponsored Dutchman Giedo van der Garde would in fact be "its test and reserve driver" in 2014.
The statement made no mention at all of Sirotkin.
"What happens now with Sirotkin?" Roger Benoit, the veteran F1 correspondent for the well-connected Swiss newspaper Blick, wondered.
"Where is there room now for Sergey Sirotkin?" agreed Mathias Brunner, a writer for German language Speed Week.
Sauber has been contacted for comment.