And now Italian newspaper La Repubblica are saying the Red Devils have offered Mertens a huge pay rise to join them in the summer.
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Dries Mertens has been in stunning form for Napoli this season
Dries Mertens Player Profile
Napoli have been trying to get him to sign a new deal for months, making him a £2.6million-a-year offer (£50,000 a week).
However, the report says United have blown this out the water with a £4m deal - around £78,000 a week - for the Belgium international.
Mertens is said to be keen to leave Italy and has reportedly also had offers from a number of Chinese Super League clubs.
He has been in the form of his life this season for Napoli operating as a striker, rather than on the left-wing.
The Belgium ace has scored 25 goals and provided 11 assists in 36 appearances in all competitions.
His contract at the Stadio San Paolo runs until June 2018.
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