David Turnbull and Callum McGregor were pictured in the training video released by Celtic yesterday.
The Scotland duo only re-joined their club team-mates on Monday after spending the bulk on June with Steve Clarke’s Scotland squad at the European Championships.
With 11 days to go until Celtic face Midtjylland in a Champions League qualifier Ange Postecoglou will be keen to have as much experience available as possible.
Mikey Johnston and Karamoko Dembele were also spotted in the video clip with neither featuring in the victory over Sheffield Wednesday.
Potecoglou is still looking to strengthen his squad, since he took charge Osaze Unhoghide is the only signing made by the club.
With travel restrictions and quarantine regulations in place time is running out for any signings to come integrate and get match time with their new team-mates before the July 20 match against the Danes.