United would likely have to heavily subsidize want-away Rashford's wages in order to facilitate a move to Italy.
Napoli could be willing to offer Victor Osimhen to United to help smooth the way for Rashford's arrival in a stunning possible swap deal.
Meanwhile Napoli's Serie A rivals Juventus want to sign Rashford's United teammate Joshua Zikrzee on loan.
Rashford reportedly earns £300,000 per week after signing a contract extension in 2023 following his 30-goal season.
He has since struggled to retain that high level of form and has often come under fire for his on and off field actions.
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Since revealing in December the want for a 'new challenge', he has not played a single minute for Ruben Amorim's side.
He was on the bench against Newcastle last week but was not used - and it remains a mystery whether Amorim will eventually bring him back into the fold.
It is a somewhat similar situation to Osimhen who made his desire to leave Napoli last summer very clear.
But after moves to Chelsea and the Saudi Pro League failed to materialise, he was frozen out by manager Antonio Conte and offloaded to Turkish team Galatasaray.
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Osimhen currently sits on 12 goals in 15 appearances in all competitions, along with five assists, a big factor in Galatasaray's eight point lead at the top of the Turkish Super Lig.
Manchester United's top scorer in the Premier League is Rashford with four goals while Rasmus Hojlund and Zirkzee continue to struggle.
Zirkzee has been fiercely criticised by pundits and fans alike since signing for £34million in the summer.
New boss Amorim subbed the 23-year-old in the first-half against Newcastle, leading to boos and sarcastic cheers from the Old Trafford faithful.
Zirkzee made a beeline for the tunnel and reports claim he is now desperate to leave United after falling out with Amorim.
Conte, meanwhile, has previously worked wonders with many former Man United players such as Alexis Sanchez, Ashley Young, Matteo Darmian and Henrikh Mkhitaryan.
Currently, Romelu Lukaku and Scott McTominay both play under Conte, with Napoli second in Serie A, level on points with first place Atalanta.
The Italian manager revived Lukaku's career at Inter Milan and has done the same for McTominay, who has become a fan favourite in the box-to-box role.
Marcus Rashford's preferred destination revealed - but January move appears unlikely
Rashford recently shut down reports about holding talks with the Stellar Agency in an attempt to accelerate a move away.
Via Instagram, he posted: "Been a lot of false stories written over past few weeks, but guys this is getting ridiculous - never met with any agency and don't have any plans to do so…"
The England star has already rejected offers to join the Saudi Pro League in January.
talkSPORT understands Rashford would be keen on a move to Spain to help revive his international career.