Real Madrid had a difficult time against 10-men Atlanta as the only breakthrough in the game came in the 86th when Ferland Mendy found the net to register an important away win in the last-16 tie.
Atlanta diminished their chances of winning against the 13-time winners when midfielder Remo Freuler was given a red card after just 17 minutes into the game for having denied a goal scoring opportunity. But Madrid, who were missing Striker Karim Benzema, Eden Hazard, captain Sergio Ramos due to injuries, found it difficult to break down the 10-men Serie A side.
Just when it looked like the game was headed for a draw, Real Madrid fullback Ferland Mendy curled the ball into the net from just outside the box after receiving the ball from a corner.
The second leg of the match will be played on March 16 at Santiago Bernabeu.