From the moment I figured he was substituted at halftime I knew something was probably, I really hope it is not serious, and you never know taking him out could just have been a precaution, I hope that was the case. Messi is too much of a price to pay for 3 points.
The coach in his press conference after the match, said it was a 'discomfort', and they didn't want to risk it, that's why he was taken off. He was probably also jetlagged as he was in Italy for the FIFA Thebest ceremony, just a night before the match. He shouldn't have started.
Ansu Fati can also help out, if he gets more playing time. I understand he's young and needs to be properly managed, but he produces chances when he plays.
Another tough match away next, every away matche is tough for Barcelona this season. I won't be expecting lots of goals from the fixture, under 2.5 perhaps.