"That's hard to say. It would definitely be the hardest decision in my career. Maybe everyone wants to play at these clubs, but I can't answer that. I think that Napoli are one of the top 10 European teams in terms of game play and performance.
"As a footballer, it's hard because you never know what comes next. I've still got a long time to go on my contract and I cannot see into the future. I'm not thinking about leaving Naples."
The Slovakia international has been at Napoli since 2007, and his contract runs until 2020.
He is widely regarded as one of the top playmakers in Europe and is a key part of Maurizio Sarri's exciting side.
Last season, Hamsik netted 12 goals and provided 10 assists, playing in every game as Napoli finished third in Serie A, per WhoScored.com.
He would be a fine addition to Jose Mourinho's United squad, bringing further creativity to an already dynamic attack.
However, Hamsik has been hugely dedicated to Napoli and his agent, Juraj Venglos, recently said he has never wanted to leave the club, per Radio Crc (h/t Football Italia, via Squawka):
Squawka News @SquawkaNews
Marek Hamsik's agent: "not everyone is like Marek. He married Napoli 10 years ago and has never wanted to move. He loves these colours." https://t.co/Ep4AAl9GxJ2017-9-8 06:01:00
Per Gladwell, the 30-year-old is just two goals away from equalling Diego Maradona 's club-record tally of 115 for Napoli.
He seems as committed as ever to Napoli as they go in search of domestic and European success in 2017-18, but United will likely keep in mind that he would be tempted by the lure of Old Trafford.