Jose Mourinho needs to lift Manchester United's morale quickly as a deflating run of performances threatens to throw their season off track completely but he faces a daunting task against a revitalised Arsenal.

Mourinho's team have not looked themselves at Old Trafford for much of the season, with their past two matches producing an insipid goalless draw against Crystal Palace and an unconvincing late Champions League victory over Swiss side Young Boys.

On their travels, they had looked as if they were getting back to form as October turned to November, with the side producing fine displays in drawing at Chelsea and beating Juventus.

Yet perhaps those performances were just papering over the cracks. United recovered from a two-goal deficit to draw at Southampton on Saturday and Romelu Lukaku scored his first club goal since September 15 but there was much to be alarmed about.

Mourinho claimed his players, with the exception of Marcus Rashford, were meek, lacking the spirit of what he called "mad dogs".

According to Duncan Castles, a British journalist with close links to Mourinho's agent Jorge Mendes, the United manager compared midfielder Paul Pogba to "a virus" after another poor performance at Southampton, saying the France international lacked respect for both his teammates and fans.

The manager's frustration at not being able to sign a top-class centre-back has been raked over repeatedly but his defensive team selection at Southampton baffled even his most loyal supporters.

With Chris Smalling and Eric Bailly unfit, Mourinho elected to play two midfielders — Scott McTominay and Nemanja Matic — in a three-man central defence against a team that had not won at home all season. It did not work.

Failure to win on the south coast further damaged United's chances of finishing in the top four — the ticket to Champions League qualification — and Mourinho himself appears to believe that is now a long shot with his team lagging eight points behind fourth-placed Arsenal.

Asked by Brazilian television what his aims were for the remainder of the season, he said: "Try to win as many points as possible and try (to achieve) almost the miracle of finishing fourth.

Arsenal, like United, spent relatively little in the close-season, bringing in Bernd Leno, Sokratis Papastathopoulos, Lucas Torreira and Matteo Guendouzi for relatively modest sums, yet look revitalised under Unai Emery's management.

They have gone 19 games unbeaten in all competitions since losing their first two matches of the season, and are playing a thrilling brand of aggressive, high-pressing football.

According to Uruguay midfielder Torreira, the manager's words are making as much of an impact as his actions — as evidenced by his half-time team talk on Sunday before the Gunners recovered to beat Tottenham 4-2.

"He told us to be calm," Torreira said. "We listened to the manager and we improved many things. That worked for us to get the victory."