Celtic defender Mark Wilson will head to America next week for a consultation in Colorado with knee specialist Dr Richard Steadman.
Wilson and midfielder Shunsuke Nakamura, who also has a knee injury, have both missed the champions’ last two matches and there are doubts over the Japan international for Wednesday’s Champions League clash with AC Milan at Celtic Park.
Injury doubts Aiden McGeady (knee), Paul Hartley (thigh) and Jean-Joel Perrier Doumbe (back) all trained ahead of the visit of Dundee United in the Clydesdale Bank Premier League.
Provisional squad: Boruc, Caldwell, Naylor, Kennedy, McManus, Scott Brown, Sno, Donati, Riordan, Vennegoor of Hesselink, McDonald, Hartley, Perrier Doumbe, McGeady, Mark Brown, Killen, Zurawski, O’Dea, O’Brien.