The Blues scored early through Fernando Torres before Aurelien Chedjou levelled for the Turkish side in the second half, setting up an expected tense affair in the return bout at Stamford Bridge next month.
Mourinho felt his team were profligate at stages as they could have scored more heavily in the opening half-hour and suggested that it will be tough to beat Roberto Mancini's men when they travel to west London on March 18.
"The result is not amazing. The situation in the second leg will be difficult," Mourinho told Sky Sports.
"If Stamford Bridge can give 10 per cent of what this public gives then that would be fantastic for us.
"We have to try and go through but it will be difficult.
"It is better at 1-1 than 0-0, so we cannot say it is a bad result, but obviously they are a very good team and it will be difficult at Stamford Bridge."
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