The former Chelsea boss has come under pressure for Los Blancos' poor performances in La Liga, but he does not think the season should be judged on the result of the two matches against the Premier League leaders.
"We have to play four competitions this season, and we won the Super Cup and lost La Liga," Mourinho told reporters at a press conference. "We're in two competitions where we can win or lose. Let's wait until the end and then we can judge the balance of the season."
Despite playing down the importance of the match for his team across the whole campaign, he did admit that if his side has aspirations of winning Europe's premiere club competition, then, getting through this round is critical.
"The last 16 is the most important round of this competition and this room full of journalists reflect what it means," Mourinho added. "We are all hoping for a good game and I know the culture of English football and Sir Alex [Ferguson] will want to play a good game."
Mourinho also believes his players will be able to step up and enjoy playing against a top side after failing to lift their games against lesser opposition domestically.
"It is easier for players to face great teams. One thing we lack is the motivation this season. It's the reason we lost points against smaller teams," Mourinho said. "In the Champions League we knew we had to be one of the qualifying teams, so kept playing at the highest level. If this means anything, under normal conditions we would have to keep it up."