There is also Monaco, this team not must be forgotten. Monaco is now also in better condition, they are currently undefeated in the domestic league after world cup. Their performance is good and they are expected to be able to compete in the European league which is their target as well. You're right, all eyes are on Barcelona vs Manchester United, I think the one team of that wins from this match will be possibility to favorite the majority of bettors.
Monaco have to hard struggle to qualified before that they were starting group stage matches with several loses even at that time Monaco has suffered lose with huge scores from Trabzonspor but Monaco can able to bounce back and finish at second position and qualified to play off matches and indeed i can see after world cup Monaco can able to improved their performance in France league that they can able to wins several times for important matches
Monaco opponent is Leverkusen and Leverkusen performance on Bundesliga also quite good even their current manager Xabi Alonso can bringing Leverkusen to avoid relegation zone and i haven't check the odds yet but probably Monaco slightly the favourite in this match and from head to head statistics Monaco had good records from Leverkusen before so lets see Monaco can managed those records and win from Leverkusen or not