#2 The left-flank of Madrid or the right flank of Barca: Where everything lies

The left flank was on fire at Camp Nou in the first leg. Nelson Semedo, Malcom, Marcelo, Vinicius Jr, everyone was doing something. The players were always running up and down the pitch. Vinicius created some good scoring opportunities but he was cursed by poor final pass. Marcelo was shut down by Malcom, smothered, to be honest. Nelson Semedo was equally good at attacking and supporting Malcom and he also defended Vinicius, especially well in the second half.
This time we might not have Barcelona's hero from the last game, Malcom, on the pitch. But we might well have Sergio Reguilon, Sergi Roberto, and Ousmane Dembele this time. Reguilon would most probably be trusted ahead of the rusty Marcelo. Although Dembele would start from left-wing on the team sheet, he would probably sway more into his stronger side while Messi would be in his free-roam position. Sergi could be used in the midfield position and he has shown the tendency to drift wide as well.
With all these players on the same flank, we except a sheer amount of pace, a lot of tackling and ball recoveries, a lot of twisted ankles too. If Messi decides to stay on that flank, then Reguilon better be ready. Reguilon's inexperience could also backfire on Madrid if he starts. Dembele is sometimes in such an overdrive that he could simply dribble past players and score. He did that against Spurs.