I never said anything about tiredness BUT since you mention it, there's provable, demonstrable evidence that teams pick up fewer points after midweek European away games...
Anyway, I wasn't going to mention that. The real answer is a combination of....Villa are a decent side full of Internationals and we were off it, we approached the game wrong, we didn't have the right intensity, the team selection was strange, we were out-worked and out-fought AND we were missing a few key players...put Bruno, Anthony, Sancho and Varane into that side and I think you have far more quality and energy.
The days of turning up to Premier League away grounds and being able to stroll through games and let your class pull you through are over. Plus, arguably there's not so big of a gap between Villa's players and ours that we can afford to be lax like there might once have been.