The Reds boast a 100% record at home so far this season and have yet to concede a goal in any competition at Old Trafford.
United brushed aside Basel in the opening game before a 4-1 win in Russia and the narrow victory in Lisbon last time out.
Marcus Rashford's free-kick extended United's winning run in bizarre circumstances to see us sit top of the group with three wins from three.
In contrast, and despite their status as the group's top seeds, Rui Vitoria's side are already eliminated having lost their last four European ties - including that 1-0 defeat at the Estadio da Luz on United's visit a fortnight ago.
They've made a positive start in the defence of their domestic title, though, and sit third in the Primera Liga with 23 points from their opening ten games.
Eric Bailly returned in the win over Tottenham after five games out and is likely to feature, but United are still without the services of Paul Pogba, Zlatan Ibrahimovic, Marcos Rojo, Marouane Fellaini and Michael Carrick.
Benfica, meanwhile, will field a makeshift defence with Andrea Almeida and Luisao both suspended, while Douglas and Jardel are set to miss out through injury.
But the visitors boast one of the most potent attacks in Portugal, spearheaded by Brazilian striker Jonas, who has scored three times in the two games since the reverse fixture.
After Anthony Martial's winner from the bench against Spurs on Saturday, the clamour is growing for Jose Mourinho to shoehorn the Frenchman into the same team as Marcus Rashford and Romelu Lukaku.
The boss hinted at giving all three a go against Benfica, and said: "We played Anthony and Rashford together against Swansea, one week ago, so yes they can play together.
"We could try again but I'm not going to say - that's no problem.
"What we cannot do is play with 12 players, and we cannot play with everybody at the same time so it is a difficult decision I have to make."
On our qualification, he added: "The main aim tomorrow is to go through.
"Ten points would be okay, but our main aim is to qualify as the number one in the group.
"Benfica will give us a difficult match, they have their own ambitions and pride and they will try to win - we want to get to the last 16 by finishing first in the group."
Form guide: United W D W L W W Benfica D D W L W W
Match odds: United 1/3 Draw 4/1 Benfica 26/4
Referee: Lithuanian ref Gediminas Mazeika will take charge of his second United game (he was in the middle for our 1-1 draw with Rostov in the Europa League last season)