United trail fifth-place Tottenham by six points and will be left with a chasm to bridge.
Without a home win in four league games, United trail fifth-place Tottenham by six points and will be left with a chasm to bridge just to secure a Champions League place if they lose.
Their preparations have been disturbed by Thursday's Europa League trip to Ukraine, where they beat Zorya Luhansk 2-0 to secure a last 32 slot, but Paul Pogba says it cannot serve as an excuse.
"When you're playing those competitions, you're playing every three days," the France midfielder told MUTV.
"We have the team to change and be ready. We have to be ready for those games. When you prepare in pre-season, it's to play those games every three days.
"We know how hard it is to play against Tottenham. We're playing at home, where we didn't win for four games, with four draws, so we just want to win this game and get to the top of the league."
Although its transport implications have provided unwelcome complications for Mourinho, the Europa League has given United some rare moments of positivity in recent weeks.
It has been particularly kind to Henrikh Mkhitaryan, who temporarily disappeared from view following his close-season switch from Borussia Dortmund.
The Armenian playmaker shone in the 4-0 win over Feyenoord and opened his account for the club with a fine goal on Thursday, having inspired United to a 4-1 League Cup win over West Ham United in between.
With United having scored just seven goals in their last eight league games -- a run that has yielded a solitary win -- he seems increasingly integral to Mourinho's hopes of salvaging the season.
"We know how good he is," Pogba said. "You just have to be confident and now he's playing more, he has more games in his legs.
"He is just getting going."
Having recently endured a sequence of one victory in 10 matches in all competitions, Tottenham can sympathise with United's struggles.
Their sticky patch ended their Champions League campaign before it had really begun and saw them slip seven points below leaders Chelsea in the title race.
But they will travel north energised by two handsome victories, having crushed Swansea City 5-0 last weekend before sinking CSKA Moscow 3-1 in mid-week to join United in the Europa League.
The stunning form of Mourinho's former club Chelsea under Antonio Conte has only deepened the gloom surrounding the Portuguese, but Spurs manager Mauricio Pochettino remains an ardent admirer.
"For me, he is the Special One and will always be the Special One," said Pochettino, who saw his side outclass United 3-0 at White Hart Lane when the teams last met in April.
"For me, he was a reference when I started my career at Espanyol. He was always very kind to me and opened his door.
"I always assess my colleagues and try to be objective. I really believe he is one of the best.
"Sometimes you struggle a bit. It's not easy to arrive at a new club, set up ideas and philosophy, but for me he was, is and will be one of the best managers in football history."
Pochettino will once again be without winger Erik Lamela, who remains in Argentina attending to his hospitalised brother, while striker Vincent Janssen has an ankle injury.
But defensive lynchpin Toby Alderweireld is in line to make his first start in eight weeks following a knee problem, having come off the bench against CSKA at Wembley on Wednesday.
United are also expected to welcome back a key central defender after Eric Bailly made his return from a knee injury in Ukraine.
Bailly's centre-back partner Chris Smalling and Luke Shaw remain out, but Michael Carrick and Antonio Valencia could feature after being rested for the trip to Odessa.