Tuesday's newspapers are linking David Moyes with a £37million bid for the out-of-favour Chelsea player, who was left on the bench for the Blues' 3-1 victory over the champions at Stamford Bridge on Sunday.
Neville insists United, who sit seventh in the Premier League, would benefit by bringing in new blood in January and can see the benefits of bringing in a big name before the transfer window closes.
But the former United full-back does not think Spain international Mata would slot comfortably into the current team.
"That's a lot of money, 37 million quid, but they need a signing," Neville said on Monday Night Football.
"Does he fit with what I would call the typical philosophy of Manchester United? I would say no.
"The first question, I think, is where are you going to play? Wayne Rooney and Robin van Persie are up top if they are fit so where are you going to play him? Are you going to play him off the left or off the right?
"We've seen Kagawa play off the left, we saw Kleberson play at times off the left, we've seen Veron at Manchester United move to the left because you can't play central midfield.
"Maybe they have to change the philosophy and maybe that's what David Moyes is thinking. Maybe he wants to play narrow wide players and maybe a three in midfield.
"They would have to change to accommodate Juan Mata in the way they normally play. They normally play with wide players. Sometimes they tuck in, but generally they have wide players and the thing for me is where is he going to play?
"He's obviously a fantastic football player, there's no doubt about that, but one thing it does do, I suppose, is that David Moyes, Manchester United and Ed Woodward need to sign a big player.
"They need to make a noise and if they get him in it will attract potentially other players - and they need three or four players.
"What it could be is the start of something to lead to other things, but typically I wouldn't say he fits."
Moyes has been linked with a host of potential targets in January and Neville identified a number of young players who would fit his former club's philosophy better than Mata.
The Sky Sports expert added: "If you took Paul Pogba, Marco Reus, Luke Shaw and Arturo Vidal - they would fit into Manchester United's philosophy.
"Lucas Moura would and Ilkay Gundogan and Julian Draxler would. They are young players who have still not reached their full potential and have the potential to go on to be world-class players.
"They are good players at the moment and that fits the Manchester United mould of how they have historically signed, more often than not."