They lost because of the pressure and they started panicking around the goal, Lunin made some good saves, but they really only had a few really clear cut chances. Everything else was cut backs and crosses to no one with every corner smashed on top of the keeper. Madrid were there for the taking and they blew it.
The pressure the front 5 or 6 players were putting on Madrid for 90 mins + is not sustainable under normal conditions. If they were really tired a few more gaps would have opened up, Madrid had 2 or 3 times in ET where they broke into spaces, that was about it.
Carvahal - that what tired looks like. All that sprinting all game and not one City player looked to be that laboured, breathing that heavily or went down with cramp.