The Red Devils decided to part company with Mourinho last week after Manchester United suffered a 3-1 loss to bitter rivals Liverpool FC last weekend.
The Portuguese coach ended his spell in charge with a fifth defeat of the Premier League season, falling further adrift of Chelsea FC in the top-four race.
Mourinho’s defence conceded 28 times in 17 games in the English top flight before his dismissal to highlight their weakness at the back.
Manchester United were linked with a number of different centre-halves in the summer transfer window but the Red Devils failed to strengthen their defence.
Toby Alderweireld was the name linked with Manchester United on a frequent basis, but the Belgium international ultimately remained at Old Trafford.
The Portuguese coach was even forced to use Nemanja Matic and Scott McTominay in defensive roles due to mounting injury problems.
Former Manchester United defender Higginbotham felt that Mourinho didn’t get enough support in the summer transfer market.
“He was let down in the transfer market — and that’s where the problems lay,” Higginbotham told The Sun.
“Mourinho was given a new contract at the start of the year and his biggest request was a new centre-back.
“United had to back him and they didn’t. He wanted to bring in Toby Alderweireld from Tottenham, but the club would not pay the fee.
“So yes, the football Manchester United played this season under Mourinho wasn’t great — but some of what Jose did is understandable.
“His limitations in defence meant he couldn’t be as expansive as he would have liked.”
The Red Devils were 5-1 winners against Cardiff in Ole Gunnar Solskjaer’s first game in charge as interim Man United manager.
The club haven’t won the Premier League title since Sir Alex Ferguson retired in 2013, although Mourinho did lead the Red Devils to a second-placed finish last term.
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