United were criticised for their approach to a Premier League clash with Liverpool on Saturday, in which they were accused of playing deliberately for the 0-0 draw.
Mourinho's side head into the meeting at Estadio da Luz with two wins from two group games against Basel and CSKA Moscow, and another victory would put them in a commanding position to reach the last 16.
However, the 54-year-old feels Benfica are the strongest side they will face – despite the Portuguese side losing their opening two matches – and insists a draw would not be a bad result in their bid to progress.
"Our sole objective is to qualify. Within that context, one point away against the strongest of the three teams in the group is a positive result," Mourinho told a news conference in Lisbon.
"But the match can also be analysed outside that context and analysed just as a match, a match we want to try to win.
"Benfica could win 12 points and finish with the same possibilities as everyone else. What I was trying to show yesterday was Benfica are much better than CSKA Moscow and Basel. I think the players were convinced in the meeting we had in the morning that results aren't the real indicator of the value of a team."
Estadio da Luz pic.twitter.com/6T15ew4caY— Manchester United (@ManUtd) October 17, 2017
Mourinho paid special tribute to Benfica captain Luisao, who remains a pivotal figure for the club at the age of 36.
"I think he has a unique career, almost unique, especially for a foreign player, who came and stayed for long in Portuguese football," Mourinho said of the centre-back.
"Honestly, I have always admired Luisao. I like the winning mentality that he always presents, and always for his loyalty and passion that he shows towards Benfica and sure enough to Portugal.
"I think he will finish his career at Benfica and I think he should. His career is, frankly, a beautiful thing."
Mourinho says he has yet to tell his players what the starting line-up will be but claims it is "easy to guess" his plans given United's injury concerns.
Marouane Fellaini, Paul Pogba, Michael Carrick, Marcos Rojo and Zlatan Ibrahimovic remain out of action, as does Eric Bailly, who sat out the Liverpool game after picking up an problem on international duty.
Mourinho added that Rojo is likely to return "in two weeks" from a knee injury sustained towards the end of last season.