The Red Devils are active in the transfer market as they prepare for Jose Mourinho’s second season in charge at Old Trafford.
Manchester United have so far concluded deals to bring in defender Victor Lindelof from Benfica and striker Romelu Lukaku from Everton.
Mourinho is thought to be keen to bring in some further reinforcements as he prepares his team for a return to the Champions League next season.
And former Red Devils defender Neville feels that Manchester United need to bring in at least two more players this summer as they gear up for the 2017-18 campaign.
Speaking to Sky Sports, Neville said: “United need to strengthen, but they all do – quite a bit.
“Even the champions need to if they’re to repeat what they did last season. You’re not just talking about winning the Premier League title, you’re talking about competing in Europe.
“English clubs have been well short in the last few seasons. All big clubs want to be winning Champions Leagues.
“That won’t happen unless they significantly improve. United need to sign four or five players.”
Manchester United enjoyed a relatively successful first season under Mourinho last season as they won the Europa League and EFL Cup.
However, the Red Devils will be hoping for an improvement in the Premier League next term after they finished sixth last season.
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