Manchester United manager Sir Alex Ferguson was in attendance as Celtic defeated Dundee United 4-0 yesterday evening.
It has been claimed that the veteran boss was there to cast an eye over midfielder Victor Wanyama, who found the net during the first half at Celtic Park.
While Ferguson has gone on the record to rule out any arrivals at Old Trafford this month, his presence in Glasgow last night has resulted in speculation that he could make a bid for the Kenyan international.
Tottenham Hotspur boss Andre Villas-Boas was also reportedly at the match. His side were yesterday linked with Celtic frontman Gary Hooper.