Los Blancos appeared to be cruising to a solid 1-0 victory at the Luzhniki Stadium courtesy of Cristiano Ronaldo's first-half strike, only to see Pontus Wernbloom restore parity with just over 30 seconds of injury time remaining.
Unsurprisingly, Mourinho was not impressed with the concession of such a late goal, but the Portuguese remains confident that the Liga leaders will progress to the last eight.
"Without doing anything out of this world, we should have been able to score a second goal," the former Chelsea boss told reporters after the game. "But it's not a bad result.
"Having led the game and conceded so late it doesn't leave a good taste in the mouth, but, at the same time, it's not a drama. I'm not happy but not all that sad.
"Last year against Lyon it was a similar situation at this stage and we managed to win the second leg at home. We're confident we can do so again this time around."
Madrid welcome CSKA to the Santiago Bernabeu for the second leg on March 14.
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