#1 Barcelona vs Atletico Madrid
Easily the most challenging game of the lot. Barcelona have struggled to beat Atletico Madrid with ease and Diego Simeone's men have the knack of upsetting the best of opposition on their day. Barcelona, meanwhile, having lost to Real Madrid on the weekend will look to bounce back and get their winning streak restarted.
Lionel Messi, Neymar and Luis Suarez were poor against Real Madrid but have been spectacular against every other team this season irrespective of competition. Against Atletico Madrid, they'll come across one of the most compact teams. Simeone's obsession of playing a compact line of defenders close to the midfield leave little or no space between the lines – the kind of space Andres Iniesta and Messi enjoy exploiting.
With Diego Godin also back for the Atleti, Barcelona's chances of progression just got a lot tougher. However, they always seem to find a way to exploit the smallest of lapses and the Madrid team have a problem of not getting back into shape fast enough. With the likes of Neymar and Luis Suarez, Barcelona have the opportunity to really taken advantage of the chaos.
Either way, this game will be a close one. The two of them are competing with each other in the Liga as well and this Champions League fixture will only further add fuel to the fire in their rivalry given how much the Catalans are trying to be the first team to successfully defend the title.
Prediction: (On final aggregate) 3-2 to Barcelona.