I don't know what happened to Atletico Madrid but in that match the Atletico Madrid squad seemed to lose their accuracy. At the beginning of the first half Atletico Madrid had a chance but well their shooting accuracy was really a big problem in the match. While Inter Milan actually also had more good chances. But we have to appreciate J. Oblak as a goalkeeper who I thought was really great in the match. Because he is always able to read the movement of the direction of the ball that will be shot by Inter MIlan players. If not J. Oblak I think Atletico Madrid could concede a few more goals. But the goalkeeper's saving action was extraordinary.
I already guessed Inter Milan would excel in the match. So this result is not surprising at all. It's just that Atletico Madrid did play below their usual performance.
Atletico Madrid have tried to do their best, but it must be admitted that Inter Milan has slightly better strength and because Inter Milan plays at home, their motivation and self-confidence is greater than Atletico Madrid.
I think Atletico Madrid's 1 goal defeat is not too difficult for Atletico Madrid to turn things around because Atletico Madrid will play at home in the second leg so they still have a chance.
Overall Atletico Madrid and Inter Milan do not have a significant difference in quality so in the round of 16 the match between these two teams is very difficult to predict.