Man Utd boss Jose Mourinho is joining the battle for Sporting CP winger Gelson Martins.
O Jogo says Barcelona and Real have been keeping tabs on the playmaker – as has Jurgen Klopp at Liverpool.
But the £52 million buyout clause might put off some suitors after the club tied him down to a lengthy contract in February.
United need attacking reinforcements after Zlatan Ibrahimovic left and they returned to the Champions League thanks to their Europa League triumph.
The Portugal international only scored six league goals last season but he laid on nine assists, the most in the Portuguese top flight.
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