Moyes, who was seated next to the press tribune, did not respond to initial questions as to why he was at the Sant'Elia stadium.

However media reports speculated the Scot travelled to Sardinia to watch Juve players likely to be involved in a swap deal that would see United striker Nani join the Italian champions, as well as Cagliari defender Astori.

Champions Juventus won the match 4-1 to claim their 11th successive win, a club record, and retain their eight-point lead over Roma.

After Fernando Llorente had levelled Mauricio Pinilla's 21st minute opener for the hosts on the half hour, Juve took the lead in the 66th minute thanks to Claudio Marchisio, who had replaced Andrea Pirlo minutes earlier.

Llorente scored his second on 76 minutes and four minutes later Stephan Lichsteiner netted to virtually seal the win.

Juve coach Antonio Conte made two further substitutions, Carlos Tevez making way for Sebastian Giovinco and Simone Padoin replacing Arturo Vidal with eight minutes remaining.