That's according to Record, which reports United are offering £57m for the Portugal international ahead of the January market.
Sporting are need of a quick sale to balance books and are now prepared to cash in on Fernandes.
The midfielder, 25, has played 10 matches and scored 5 goals so far this season.
Fernandes stated just last week: "Since 2016, there's been talk about my possible departure.
"I'm well, doing my job and doing the best I can. I have dreams to fulfill but I have no need to force my departure.
"I feel the love here and if I have to leave, I hope I leave good memories."