What you were saying was true. MU has very bad record against Barcelona. MU was so difficult to beat Barcelona. Xavi has raphinha as a replacement for dembele. Raphinha has proven itself during the match against real betis. I think that there should not be a problem with barcelone even playing without dembele. Barcelona is feeling so good with the composition of the current squad. I think that this gonna be a game that may not able to be won by united. It's still a match that can't be determined easily
However it is, Dembele's injury is going to be a problem for Barcelona. He's the most creative attacker they have and he will be missed. The odds of the game favor Barcelona not only because of history but i believe Barcelona are in a better place than Manchester United. Despite the good result from United lately you can see that the players are still struggling to really play the kind of football he wants from them, they choke against formidable opponents at times. There is still a lot of room for improvement in Barcelona but the players already understand what Xavi wants from them, its the execution that's a problem. I don't think it going to be a match won by individual brilliance, it's going to rely more on the coaches tactics.
Dembele's hamstring injury is very detrimental for Barcelona that we know his speed to dribble is beyond doubt and as a right winger he has played quite well this season. But indeed he is doubtful to appear when he meets Manchester United later, but that has been resolved by Xavi and the temporary Dembele position will continue to be filled by Raphinha or Ansu Fati until Dembele has recovered from injury. So barcelona will probably still put up a tough fight against manchester united and I think it will be even more interesting.