A few remarks.
It was visible they had more rest, simply more energetic throughout the match. Kept their intensity in the 2nd half. Messi and Suarez facing their frontline (often in 2 vs. 3 situations) couldn't do much. And even if they did, they were no thought balls. In my opinion, we were individually underwhelming, Busquets, Rakitić, Arthur, Messi, Lenglet all did worse than expected. Usually, there's a well-established mechanism - Busq drops between the CBs so they can venture wide which together with Suarez stretching their backline opens passing options for players in halfspaces, namely Coutinho and Messi. Where did it go wrong last time? Think 2 important factors are to be considered. (1) the aforementioned individual level of Barca's 11 (almost none of the players involved in that scheme did well last night) (2) FBs. Semedo did have a great game, neat passes, dribbles and that great chance he created for Suarez. But at the bottom of it, there's a difference between him and Roberto. While one is a (no doubt about it) better FB, the other one makes a better fake midfielder. In other words, Busq dropping deep left Raki and Arthur alone and they didn't have Semedo by their side. Few times they did, we instantly looked better and in control. Don't think he provided enough width. Although defensively did his job, probably the reason he stayed on the pitch.
Already said that subbing in Malcom would've been my move. Valverde went for Roberto, a more defensive sub, which did provide energy. Just like Vidal's one. Good subs, but with a winger we could've damaged them seriously.