In all, United boss Jose Mourinho makes four changes to the side that were held to a goalless draw at Liverpool over the weekend, with Rashford and Mata coming in for Anthony Martial and Ashley Young respectively.
The other two changes come in defence, with Daley Blind replacing Matteo Darmian at left-back and Victor Lindelof replacing Phil Jones as partner for Chris Smalling in the middle. Antonio Valencia is on the right and David de Gea continues between the posts.
As for the hosts, Rui Vitoria makes five changes from the side that managed a 1-1 draw with Maritimo in the Primeira Liga at the start of the month.
In the back four, Andre Almeida is suspended after his red in the 5-0 humiliation at Basel last month, while Jardel misses out with a back problem, meaning recalls for Douglas and Ruben Dias alongside Luisao and Alex Grimaldo.
Benfica: Svilar; Douglas, Dias, Luisao, Grimaldo; Fejsa, Augusto, Pizzi, Salvio; Goncalves, Jimenez
Subs: Julio Cesar, Lisandro Lopez, Samaris, Zivkovic, Cervi, Jonas, Seferovic
Manchester United: De Gea; Valencia, Lindelof, Smalling, Blind; Herrera, Matic; Mata, Mkhitaryan, Rashford; Lukaku
Subs: Romero, Darmian, Jones, McTominay, Lingard, Young, Martial
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