Argentina striker Diego Milito gave the Serie A leaders a 1-0 advantage in their Italian Cup semi-final first leg against Fiorentina at the San Siro on Wednesday.
However, the perfectionist coach said they would have to buck up their ideas with the Champions League first knockout round first leg at home to the London club looming on February 24.
"Yes we can beat Chelsea. Yes we can but not like this no," Mourinho told Reuters having again clashed with temperamental forward Mario Balotelli during the Fiorentina game.
"There have been too many passes gone astray, not enough clarity in our play. It hasn't pleased me that we haven't had continuity in our performance."
Inter's league game at Parma last weekend was postponed because of snow and in their previous match at home to Juventus in the Italian Cup quarter-final, Mourinho's side had to come from behind to prevail 2-1 with a last-minute Balotelli strike.
Despite inconsistencies in their displays, Inter keep on winning and are eight points clear in Serie A as they seek a fifth straight scudetto.
BIG TARGET
The leaders entertain Cagliari on Sunday but the Champions League remains the big target and after losing to Manchester United this time last year, Mourinho comes face to face with beloved former club Chelsea.
Experiencing a first-leg encounter in the Italian Cup is good preparation for the European clash even if the second leg against Fiorentina does not take place until April 14.
"It was good enough. We could play better but 1-0 is always a positive result when you play in two legs. It's a pity we have to wait two and a half months to play the second leg," added the Portuguese coach.
"But in a semi-final I believe 1-0 is a good enough result to give us good hope and a good chance to be in the final."
Mourinho, who was close to Chelsea skipper John Terry while winning the 2005 and 2006 Premier League titles at Stamford Bridge, opted not to answer a question about recent allegations over the England captain's private life.
