The Blues boss believes Bayern Munich along with Real Madrid and Barcelona are the outstanding favorites to triumph in Europe's elite club competition this season.
The Portuguese guided Porto and Inter to Champions League glory, but failed to win Europe's premier club competition in his first spell at Chelsea or during his Real Madrid tenure.
The London club has already qualified for the last 16 of this season's competition despite defeat at Basel last time out and will win Group E should it beat Steaua Bucharest on Wednesday night.
Bob Paisley is the only manager to win the European Cup three times and Mourinho does not expect to emulate the Liverpool legend's feat next May.
"Our chances this season, which is my first season [back at Chelsea], are not comparable with chances other clubs have," Mourinho said. "Other clubs have completely different stability, squad and evolution of teams to be considered favorites to win.
"We reached the last 16. If we reach the quarterfinal, which is the next step, I used to say every team in the quarterfinal has a chance to win. But in my analysis we are not one of the favorites."
European champions Bayern Munich have displayed ominous form again this season and Mourinho believes the German giants, Barcelona and his former club Real are the teams to beat.
"Bayern is European champion and a top club. They have a new coach [Pep Guardiola] but the same players, same team. Barcelona and Real Madrid also. These teams clearly [are among the favorites] in terms of potential and responsibilities," he said. "But I say other teams are very strong. One of these teams arrive in the last eight and then anything can happen. Manchester City, Manchester United, Atletico Madrid and Chelsea.
"In the 16 we find some difficulties to cross because some important teams can finish second [in their group]. You can have City, Dortmund, Juventus. Teams can finish second that can beat anyone of the first teams, so it is an interesting competition as always."
Mourinho also revealed left back Ashley Cole will start against Steaua at Stamford Bridge, and he will make further changes from the side that was beaten 3-2 at Stoke City on Saturday.