It will be interesting to see how Klopp approaches this game. Normally he chooses a pretty cautious tactic in tough away games in Europe, and it seems like a natural approach to stay low and use our pace on the counter. But I wouldn't be chocked to see a high press in the beginning, to try to get Barcelona stressed. I think they're too skilled and experienced for that to pay off though.
Similarly, he could go with a number of different midfield combinations. I hope he dares to give Keita the chance. Playing Keita and Henderson as 8s has given us the most creative midfield performances this season, and they are both excellent in defense as well.
Everyone seems to expect an explosion of chances and goals, but it will be two teams with a massive respect for eachothers' attacking players. Both teams like to push their full backs high, but will they dare to in this game? I can imagine a pretty slow game, with two teams that are excellent in keeping possession.