It will be second against third when United welcome Liverpool to Manchester, with Mourinho's men two points clear of Jurgen Klopp's high-flying Reds.
The strengths of both teams are contrasting — United boasting the second-best defensive record, having only conceded 22 goals in 29 matches, while Liverpool's prolific attack have netted 67 times, only second to champions-elect Manchester City.
While acknowledging United's own weaknesses, Mourinho highlighted Liverpool's vulnerabilities.
"They are a very good team, but they are a very good team with some weaknesses," Mourinho said. "Weaknesses I don't think is a very strong word because I also use that word in relation to my own team.
"They are not the perfect team. I think they are a very good team and that is why they are where they are in the Premier League, which is difficult.
"They have qualities and they have weaknesses. We have qualities and we have weaknesses.
"One of my good qualities as a coach was always to know very well my team's weaknesses. Sometimes I try to hide them and sometimes I have to try to compensate for them with other things.
"We are very similar in terms of points in the Premier League. Liverpool have already qualified for the Champions League quarter-finals and we still have 90 minutes of a big fight to try to be there.
"So in the Champions League they are clearly ahead of us, but in the FA Cup we have a chance they don't have so we are having quite similar seasons."