According to Italian newspaper Il Mattino, the Red Devils have held secret talks with Dries Mertens over a potential summer move.
Belgian ace Mertens has hit 23 goals for Napoli this season, having moved into a central striking role.
The 29-year-old is out of contract in 2018 at the Stadio San Paolo however, and is said to be stalling over a new deal as he explores his options.
Mertens is said to have met with United representatives for two hours in the lobby of a hotel in Naples earlier this week to discuss a potential move.
Jose Mourinho hails performance on 'awful' Rostov pitch
Jose Mourinho hailed his Manchester United fighters after claiming they were forced to play on an “impossible pitch”.
Henrikh Mkhitaryan's away goal has given United the upper hand in the tie ahead of the return leg against Rostov at Old Trafford next Thursday.
And even though United conceded an equaliser, Mourinho praised the character of his players for coming through such a tough test on a dodgy surface.
“We go home with a positive result,” said Mourinho. “It was a very good performance in relation to the conditions.
“It was impossible to play better, impossible to have the ball, impossible to play a passing game, so we played what the game demanded and we played well."
Fellaini blasts back at Carragher
Marouane Fellaini has described Jamie Carragher as a “world champion leg breaker” in response to criticisms from the Sky Sports pundit.
Carragher last year wrote that he ‘hoped we don’t see his elbows in England again' following a ban for the Manchester United midfielder for elbowing Leicester’s Robert Huth.
Carragher has since clarified his comments, insisting he hoped the Fellaini was moved on to another Premier League club rather than out of the country.
But Fellaini told Sport/Foot magazine “If I am violent and aggressive, what was Carragher?