When I look at the matchups I think that the most difficult to predict result can the Napoli v Barcelona and Inter v Atlético Madrid. I mean theory there are favourite of this matches which is Barcelona and Inter. You know Barcelona are having really tough days and Xavi even announced his parting ways with Barcelona this summer. Napoli could make a surprise. Also, Atletico Madrid plays very consistently in Laliga as well as Inter Milan in Serie A, so these two clubs will play carefully, aggressive and defensive, play both of them are equally good.
Aside from this four-team matchup, every other game in the Champions League round of 16 is easy to predict. This matchup features two big teams that are both performing exceptionally well in their respective leagues, making it difficult to predict who will win the game. In the meantime, I'll have to wait for the first leg of the Champions League games between these teams to see who has a better chance of winning against the other. It will be an extremely difficult decision. Their individual team brilliance will speak for itself when they meet to play soon.