A Danny Welbeck header from a corner was cancelled out by an equally impressive headed finish from Cristiano Ronaldo in the first half, but neither side could find a further breakthrough on Wednesday evening.
And, despite United effectively holding a one goal lead courtesy of the away goals lead, Mourinho confidently predicted his side can cancel that out at Old Trafford.
"I think they gave everything," Mourinho told Sky Sports after the match. "But again it was difficult because we started off well. Fabio [Coentrao] had a really good chance when he hit the post, then the first time they go in our half they score a goal out of nothing.
"To be losing 1-0 is not a good situation. After halftime they tried but Man U played for the result. Their defense was deep but now it is our time to go to Old Trafford and I think 1-1 is not a bad result because everything is open and we can score more than one goal there."
The former Chelsea boss was not surprised with how the match went, saying he expected the clash to be open and he still thinks it will go right down to the wire in the second leg at Old Trafford.
He continued: "It was nothing new. It was not a surprise. It was basically what I was waiting for, which is everything open for the second leg and I was thinking this will go to the last minute."
However, Mourinho did not predict how United set up, highlighting how deep the visitors' defenders were, claiming Rio Ferdinand and Jonny Evans did not even set foot in the Madrid half after halftime.
They changed the way they play. They played very deep in the second half. I don't think Rio or Evans put a foot in our half. I think they were waiting our set pieces so they could counterattack for the second goal, but we kept them out.
"Normally that would change the game, but they did well. THe result is open if you ask me a percentage, I wouldn't change my thoughts. It is still 50/50."
United's gameplan in the second period suggested it was waiting for chances to catch Madrid on the counterattack or win cheap set pieces. Mourinho noticed this and felt his players were the one actually looking to press for a win.
"They [United] had to be champions in the second half and champions out of context because we were chasing the game and they were waiting for an opportunity, but this is the CL. It is two games home and away and they did played their game and they did it well."
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