The Blues have enjoyed some fantastic results this season, including a 6-0 win over Arsenal, as well as home victories over Manchester City, Liverpool, Manchester United and Tottenham Hotspur.
However, the Stamford Bridge outfit have lost three of their last five fixtures in all competitions - a run of results that has left them as third favourites to win the Premier League and needing to overturn a 3-1 deficit against Paris Saint-Germain in order to reach the semi-finals of the Champions League.
"I don't know if we are going to have a fantastic performance or not," Mourinho told reporters. "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."