Celtic are making no comment over a newspaper report that appears to show captain Scott Brown apparently drunk in Edinburgh days before a cup final.
The Sun published pictures of the Scotland captain slumped on the pavement on Wednesday night.
Brown, 29, had the day off on Thursday and was back training on Friday morning.
Celtic play Dundee United in Sunday's Scottish League Cup final at Hampden Park.
Manager Ronny Deila has previously spoken of the need for his Celtic squad to be "24-hour athletes" and has introduced strict rules over diet.