Speaking on Sky Sports, Neville said: "If you'd said to me seven or eight days ago whether Rashford could leave in January, I'd say no chance.
"One thing in the past with players at a big club, if you're talking to me about it every single week, it becomes a distraction for the manager and the focal point of the press conference, that's when it does become obvious they have to leave."
He added: "It'll probably work for both parties. There's good examples of players who have struggled at Man Utd and gone on to do better elsewhere - Jadon Sancho at Chelsea, Scott McTominay didn't struggle but he's doing well at Napoli.
"Marcus might think that's the right thing for him as well."