The reason wasnt the lack of quality. Its Motivation!! Nobody had motivation to play yesterday. They started to try when the match was already loss....
Maybe not empty motivation, but lack of fighting spirit, I presume due to tiredness also. Also perhaps, they have been instructed to focus on defense, and some couldn't quite cope with it.
I have just watched first half properly. Yesterday I couldn't watch more than 10 minutes of the game due to technical error and here's what I think.
1. Roma played high pressing, tight defending and long balls. Dzeko in particular has been outstanding in winning the air and outmuscle pique and Umtiti in many occasions. Schick, Nainggolan, De Rossi has been doing excellent in recovery and physical clashes, also making run and trying key passes. Every roma midfielder perform, actually, consistent pressing etc. And for Pique, he was still great at clearing and doing tackle at some occasions (hence Roma didn't score more than one goal in the first half), but really lacking it when in aerial duel or physical brawl with Dzeko (this man was the main danger last night, honestly). Why didn't Pique or Umtiti for this instance be like Fazio in the other side. Suarez had a "heavy" day being climbed in the back in numerous occasions. At least it would make him less active.
2. When we are defending we let Roma players did the movement. Like Rakitic in several moments just stand there between Roma players like anticipating for a break pass. He should concern more about players movement or covering pass line rather than stand still waiting for a break pass from Bob.. He's not Messi.
3. Messi has been below his average. Granted, not really having team mates to help in tiki take ing. Iniesta honestly doesn't have the stamina to play with him anymore, and the others, beside Alba and Suarez are not as quick as he wanted to be. And they're busy in their own post last night. Alba concentrate at the back and Suarez is lonely, shadowed by Fazio and co. Messi has a decent moment in the beginning though, his key pass to Roberto was wasted by the latter. And his freekicks have been off, strangely. Roma players making noise (refusing to step back) during freekick helped ruining his concentration too I think.
The point is, we let Roma played the way they wanted, and leaving us defending for aggregate. And it's also EV's fault for not bringing Dembele for Iniesta or Roberto earlier as it was only him that I can thought would be able to ruin Roma formation with his run, and able to do some forward play with Messi and Suarez.