The Red Devils slumped to a chastening 3-1 loss to defending Premier League champions Manchester City at The Etihad last Sunday to highlight the increasing gap between the two clubs.
Goals from David Silva, Sergio Aguero and Ilkay Gundogan helped Manchester City to ease to a comfortable victory, while Anthony Martial netted what turned out to be a consolation goal from the penalty spot.
The 20-time English champions are in eighth place in the Premier League table and 12 points behind defending champions Manchester City after 12 games in the top flight.
Of most concern to Mourinho will surely be their poor defensive record, having conceded 21 goals in 12 games in the Premier League this season.
Indeed, only Cardiff City, Fulham, Burnley and Huddersfield Town have conceded more goals than the 20-time English champions in the Premier League.
Manchester United have been linked with number of potential defensive recruits ahead of the January transfer window.
Notably, big name players such as Alexis Sanchez, Romelu Lukaku, Fred and Eric Bailly have all struggled for confidence and form to give Mourinho another headache.
The Portuguese head coach has spent in excess of £400m on new signings since Mourinho took over the reins of Manchester United from Louis van Gaal.
However, the former Chelsea FC manager is still relying on some of the players signed under David Moyes and Van Gaal – and even Sir Alex Ferguson.
Former Manchester United defender Neville admitted that he is unsure what areas need to be tackled first in the Red Devils team such is the current conundrum at Old Trafford.
“Even with the players he is bringing in, he is still stuck with the players from previous managers,” Neville told Sky Sports.
“It’s a question for Jose Mourinho, where do Manchester United sit? And it’s not a case of finding a final piece of the jigsaw and all of a sudden they are going to win the league because at the moment the jigsaw is half-empty.
“When you look at it you’re not even sure what pieces are missing and that’s something the board, the senior scouts and coaches have to sit down and work out.
“They finished second last season which was the best finish since Sir Alex Ferguson. It’s so confusing watching Manchester United because you don’t know what or who to change.
“Jose Mourinho has won wherever he has been – he has won 20 titles, my point is: David Moyes couldn’t sort out the group, Louis van Gaal couldn’t sort out the group and now Jose Mourinho, the most successful manager, can’t sort out the group.”
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