Manchester United must move heaven and earth to keep David de Gea from joining Real Madrid or sign a player from the 10-time Champions League winners as a compromise for losing their inspirational goalkeeper.
De Gea has arguably been United's player of the season, with a string of man-of-the-match displays prior to the club's recent six-game winning run helping build the foundation to their run in the Premier League top four.
Recent reports have suggested United would be willing to allow De Gea, whose current contract expires in 2016, to leave the club only if Gareth Bale moved from Real Madrid to Old Trafford as part of the deal.
And Neville has said that type of deal is the only compromise United should make otherwise they risk manager Louis van Gaal's new era at the club being dismantled beyond repair.
"United need to try and keep him," Neville told Sky Sports. "If they're not going to keep him, there's only one club you can think of that is going to come in for him [Real Madrid]. United have got to take someone off them.
"He has settled down now and is performing fantastically well. He's been the best player for United all season, and he's a candidate for player of the season. When this club - and any club for that matter - don't have the goalkeeping position settled, it creates anxiety and nervousness all the way through the team."
Victory over Manchester City all but secured the club a return to Europe's top tier club competition for next season, a potential carrot for De Gea who is yet to agree a new deal.
Speaking in March regarding the potential prospect of not qualifying for Europe, De Gea said: "We have to qualify for the Champions League, no matter what. We already missed out last season and a team like Manchester United cannot do that two years in a row."