Dembele's absence if it is true and not just a tactics will give Arsenal more advantage to win that game which they have to take. Arsenal are doing better already without Odegaard, they have adjusted and that should not a problem for the team anymore. Any result other than a win from that game will be considered a disappointing result for Mikel Arteta's team.
 Barcelona also have a big job to do tomorrow as well. They have to be very good and try not to get a red card.