Neville told Press Association Sport: “If I was Luke Shaw, I wouldn’t be looking to get out of Manchester United.
“I’d be looking at that situation thinking that on Saturday (Mourinho) played Ashley Young at left-back, that he has been playing Matteo Darmian at left-back, Marcos Rojo, Daley Blind. These are players who are not out-and-out left-backs.
“So rather than thinking ‘the manager doesn’t rate me’, I’d be thinking ‘I have to pull my finger out here’ and think the opportunity in front of me is absolutely huge, to be the number one left-back at one of the biggest clubs in the world.
“Something has to change for Luke Shaw, because someone with that ability has got to be England and Man United’s number one left-back, and if he’s not, then there is something fundamentally wrong.
“The comments coming from Jose Mourinho suggest there may be an attitude problem or a professionalism problem, and if that is the case, this could be the kick up the backside he needs.
“He needs to probably take a long hard look at himself and realise the opportunity that is in front of him.
“In life, you only get one opportunity at a club like Manchester United, and if you don’t grasp that opportunity, you end up being sold and going maybe back to (Shaw’s previous club) Southampton, thinking ‘should have, would have, could have’.
“I think it is at that point now for Luke Shaw where it is time to deliver and become the player that I believe he can become.
“Because I watched him pre-Manchester United and I thought he looked like a Manchester United number one left-back. He was a sensational player, and can still be a sensational player.
“But there is obviously something not quite right with him at this moment in time and I find it sad.”