Manchester United were again represented on Thursday for Porto's draw with Eintracht Frankfurt on Thursday.
The Daily Mail says United went to go and watch Eliaquim Mangala on Thursday night and are braced for a straight fight with rivals Manchester City for his signature.
United manager David Moyes has identified the France international as a player worth pursuing as he begins a major reshuffle at Old Trafford.
City will make another attempt to sign Mangala in the summer despite abandoning a joint £35million bid for him and team-mate Fernando.
