Tuttomercatoweb reports that the Serie A champions are likely to sell McTominay rather than risk losing him for nothing when his contract expires in 2028.
The Scotland international joined Napoli from Manchester United in 2024 and played a key role in their Scudetto triumph the following year.
However, he turns 30 in December and Napoli could view next summer as their final opportunity to secure a significant fee for him before his contract enters its final year.
A contract extension is also considered unlikely, with McTominay reportedly seeking wages of around €8 million per year.
Manchester United and Aston Villa are both said to have made enquiries about the midfielder during the summer, although no formal offer has been reported.
Tuttomercatoweb values McTominay's potential transfer at between €25 million and €30 million.
Villa would offer McTominay a route back to the Premier League, while the midfielder already has a connection to the club through Scotland captain John McGinn. The pair have played 63 times together for their country.
McTominay has established himself as an important figure at Napoli since arriving from United, but the Italian club could now decide that the financial opportunity presented by a summer sale is too good to ignore.
Napoli have a number of options in midfield, although the club's decision will ultimately depend on whether McTominay's contract situation can be resolved.
For now, the Scotland international remains under contract in Naples until 2028, but a sale next summer is increasingly being presented as the most likely outcome.
A move would bring to an end a three-year spell in Italy for McTominay and could put him back on the radar of Premier League clubs looking for an experienced central midfielder.
Aston Villa's previous interest means they could be one of the teams to watch if Napoli make the 29-year-old available.