New Real coach Zinedine Zidane went with Keylor ahead of Thibaut Courtois.
"I'm delighted because I was hungry to get back playing. I've worked with real intensity and we're thankful and very satisfied. Zidane gave me his support and put his faith in me in his first spell here and he's given me the chance to play in his first game back. I'm going to work very hard to be available to him," said Keylor.
"Every coach has his way of doing things. Zidane has chosen the line-up he thought was best for today. We all went out there, tried hard and played our game. A player reaches his best levels on a game-by-game basis and that's how we win matches. We've only had three training sessions with him and there's been a great feeling around the place. He gave us a talk to explain how we were going to play.
"Every player knew that if we wanted to keep a clean sheet, they'd have to put in their best efforts."