Victor Wanyama headed in his eighth goal of the season in front of the watching Manchester United manager Sir Alex Ferguson as Celtic battered Dundee united 4-0.
Ferguson was scouting Wanyama, 21, as he seeks to ease United's midfield malaise, which is lacking an outstanding defensive option.
Wanyama nets Celtic's second against Dundee United
With Darren Fletcher ruled out for the rest of the season and his future in doubt, Ferguson may this year sign a central midfielder for the first time since July 2007.
Wanyama has been identified as a more suitable option than the versatile Phil Jones, viewed long-term as a centre-back, to complement Michael Carrick and Tom Cleverley.
Wanyama celebrates his header
The Scot has decided to stay behind in Britain as his United squad endure some warm weather training in Qatar ahead of Saturday's FA Cup fourth-round tie with Fulham.
Although Ferguson will today attend the funeral of Celtic legend Sean Fallon, a former player and assistant manager to Jock Stein when the club won the European Cup in 1967, it is likely he is attempting to secure the signing of Crystal Palace winger Wilfried Zaha as well.
Also in attendance at Parkhead was André Villas-Boas, amid rumblings Tottenham are considering a bid for Celtic's English striker Gary Hooper.
Hooper celebrates his goal
Hooper, 24, scored twice in Bhoys' Tuesday night victory to take his tally for the campaign up to 21.
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