Arsenal the last few years have faced Milan, Barca, Bayern Bayern in the Round of 16. Not a good example that. Benfica and Porto, yes, but they're also depleted every year by sales of their key players. Again, turning this argument into experience is the only important aspect is pointless, that was not what i meant at all. the other factors like quality and luck is important but take Chelsea (2012) for example. Even when we were the worst side in the competition, the team had the know-how to hang on during a tie and win it in decisive moments Atletico have been a machine this season but how many games have they played the last few years with the stakes anywhere close to a Champions League semifinal match? Not many. Even PSG in the quarters had the quality and the luck in the first leg but in the last 2 years they've played just 4 games of real high stakes (Barca QF in 2013 and Chelsea in 2014). In the 2nd leg, PSG capitulated. Stamford Bridge is a tough place to visit in such situations and they couldn't hang on. Experience and mental strength is not exaggerated at all