The Premier League side are currently top of Group A, having won their first two matches against Basel and CSKA Moscow.
Benfica, meanwhile, have lost their first two games against those same two sides, but Mourinho thinks that the Portuguese outfit are the "strongest" of their three group opponents.
"Our goal is to qualify," Mourinho replied when asked at a press conference if a draw in Lisbon would be a decent result. "If we are able to qualify before the last match, the goal becomes finishing first. Currently our sole objective is to qualify.
"Within that context I think that one point away against the strongest of the three teams with us in the group is a positive result. But it's a match we want to try and win."
Mourinho went on to suggest that reporters could probably guess his starting XI as "our options are so few".
"I will not tell you the team - first because the players don't know yet," he added. "Second, with so many injuries that should be something you can [predict] with a guarantee of success because our options are so few."
After the trip to Benfica, Mourinho then takes his side to Huddersfield Town in the league on Saturday afternoon.