The Red Devils were held to a 2-2 draw with Southampton at St Mary’s on Saturday evening to lose more ground on their traditional rivals.
Goals from Romelu Lukaku and Ander Herrera helped to level the Premier League clash following a disastrous showing in the opening 20 minutes at St Mary’s.
Manchester United are eight points adrift of fourth-placed Arsenal ahead of the clash between the bitter rivals at Old Trafford on Wednesday night.
The Red Devils have already conceded 15 times in 14 games in the Premier League this season to underline their defensive frailties.
Manchester United are level on points with fifth-placed Everton, who suffered a 1-0 loss to Liverpool FC in the Merseyside derby at Anfield on Sunday evening.
Former England defender Neville believes Manchester United are battling to secure a Europa League spot rather than a place in the Champions League.
“If you are Manchester United, where are you at? Watching them on Saturday against Southampton they look a million miles away from [Arsenal and Tottenham],” Neville told Sky Sports.
“United are in a massive battle to get into the top four, even the Europa League places at the moment.”
Only Fulham, Burnley, Huddersfield Town, Southampton and Cardiff City have conceded more Premier League goals than Manchester United in the current campaign.
The Red Devils have lost to Brighton, Tottenham Hotspur, West Ham United and Manchester City in the current campaign.
Manchester United have also drawn four games to endure a stop-start season under the Portuguese head coach.
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