The Blues beat Arsenal 6-0 - following on from home wins this season over Manchester City, Liverpool and Manchester United - but a week later lost at Crystal Palace before falling to a 3-1 Champions League quarter-final first-leg loss at Paris St Germain.
"I don't know if tomorrow we are going to have a fantastic performance or not," said Mourinho, whose side were beaten in the reverse fixture in December.
"Part of the stability of the top teams, of the teams full of people with experience, is exactly that stability.
"We are the team that during the season we have ups and downs. We have players that were not capable to keep a platform of stability in their performances. We had a few players with these ups and downs."
Mourinho was scathing in his criticism following the Selhurst Park loss and Fernando Torres was omitted from a striker-less starting XI at PSG on Wednesday, even though Samuel Eto'o (hamstring) is injured.
Mourinho insists Torres has a future at Chelsea, despite wanting more from the much-maligned World Cup-winning Spain striker.
The Portuguese added: "Since the beginning of the season we tried and we thought about the possibilities of different qualities. Different strikers, different qualities.
"Fernando is a player with a certain profile and will always be the player with that profile.
"It's not at the age of 30 years old that he's going to add new qualities to the qualities he has.
"He gives what he can. We respect that. I respect that. That's why he keeps playing, we keep trusting him and we believe that he still has things to give us."
Mourinho pursued Wayne Rooney during the 2013 summer transfer window, but the striker has since committed to Manchester United.
Chelsea decided not to chase a striker in January and prioritised other areas of the team, but will aim to sign a proven goalscorer this summer after carefully assessing their options, with Atletico Madrid's Diego Costa hotly linked.
It will not be the first time Chelsea have spent big on a striker, with Hernan Crespo, Adrian Mutu, Andriy Shevchenko and Didier Drogba recruited at great cost and only the latter an overwhelming success.
Mourinho added: "Chelsea can be considered very successful with strikers. Didier Drogba was a Chelsea striker for eight years.
"(But) it's the most difficult position to adapt."