Twice European champions Benfica face a stern test at home against a United side who have burst out of the blocks in their Premier League title defence with a 100 percent record and lead the table on goal difference.
Still, Benfica coach Jorge Jesus believes his team can grab points if they are able to adjust their attack-minded tactics to counter United's flowing attack.
"We want to be stronger tactically, if we manage that, we will balance out the match. There are three points on the table but in the Champions League every single point is important," said the Portuguese coach.
Benfica, knocked out at the group stage last year, will be confident of progressing this time given the other teams in the group, Switzerland's FC Basel and Romanian debutants Otelul Galati, look very beatable.
"We have to approach this game differently in terms of tactics and objectives. United is one of the best in Europe and has top players but we also have them," Jesus added.
Manchester United striker Wayne Rooney will be looking to translate his rampant domestic form into Champions League goals. The England forward has scored back-to-back hat-tricks in Premier League games, the latest coming in Saturday's 5-0 thumping of Bolton Wanderers.
"It's down to maturity," manager Sir Alex Ferguson said of Rooney, who has notched eight league goals.
"He's in his mid-20s and I always think when players get to this age they get more authority in their game, their timing is better and their control of games is better. His presence is getting bigger in every game. He's looking fantastic."
Benfica's backline, much-improved from last season thanks to the signing of centre-back Ezequiel Garay from Real Madrid and goalkeeper Artur from Braga, will have to be at the top of their game to stop Rooney and deny room for Nani and Javier Hernandez to inflict damage.
Belgian midfielder Axel Witsel has also arrived to make Benfica's midfield more compact, freeing playmaker Pablo Aimar to assume a more attacking role,
Up front, the Portuguese's side's main weapon remains the efficient Paraguay striker Oscar Cardozo, while Spanish forward Nolito has brought added speed and mobility.
Benfica: 1-Artur Moraes; 14-Maxi Pereira, 24-Ezequiel Garay, 4-Luisao, 3-Emerson; 20-Nicolas Gaitan, 28-Axel Witsel, 6-Javi Garcia, 10-Pablo Aimar, 9-Nolito; 7-Oscar Cardozo.
Manchester United: 1-David De Gea; 4-Phil Jones, 12-Chris Smalling, 5-Rio Ferdinand, 3-Patrice Evra; 18-Ashley Young, 8-Anderson, 16-Michael Carrick, 17-Nani; 10-Wayne Rooney, 14-Javier Hernandez
Referee: Damir Skomina (Slovenia)
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