In a pulsating game in the Santiago Bernabeu, Danny Welbeck headed United in front before former Red Devils star Cristiano Ronaldo pulled Real level.
Both teams had chances to win it in the second half and, ahead of the return meeting at Old Trafford in three weeks' time, Mourinho believes it is 50/50 regarding which team will progress to the quarter-finals.
"It was not a surprise the match or the result," Mourinho told Sky Sports 2. "I think it was basically what I was waiting for which was everything open, very open for the second leg. I think this will go to the last minute.
"If you ask me the percentage, I don't change one single number, it's 50/50. We can score more than one goal there."
When asked if it was a tactical game, the Real coach replied: "For them, not for us. Tactically they changed their way of playing. I think Rio Ferdinand and Jonny Evans didn't put one foot in our half.
"I think they were waiting for a set-piece or a counter attack to score a second goal. We were the team that was chasing the game and they defended well. The result is open.
"They had two big chances in the second half but the chances were out of context because we were chasing the game.
"They were just defending and waiting for a situation. But this is the Champions League, two matches home and away. They did their match and they did it well."
Real's season has been beset by reports of player unrest, but Mourinho was pleased with the response of his team after falling behind to Welbeck's goal after 20 minutes.
He continued: "I think they gave everything. Of course, it was a difficult game because we started strong and had a real big chance when Fabio (Coentrao) hit the post.
"The first time they go in our half, they score a goal out of nothing and psychologically to be losing 1-0 is not an easy situation.
"After that, in the second half they tried everything. It's time to go to Old Trafford. I think 1-1 is not a bad result because everything is open and we can score more than one goal there."
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