Celtic and West Ham United legend Frank McAvennie expects Fraser Forster and Virgil van Dijk to leave the Hoops.
The pair are being linked with Southampton and are likely to leave should Celtic be dumped out of the Champions League by Legia Warsaw.
McAvennie said: ''I'm worried about the season if they don't get through on Wednesday. The fans are only going to take so much if the club is not investing.
''If they don't win on Wednesday I think they will lose van Dijk and Forster, and from what I hear there's a few more want to leave.
''Celtic have got to invest. I don't know who Ronny Deila is.
''I'm worried about Celtic because this is not the Celtic I know."
