Actually, Manchester United will be more enthusiastic when playing at home with a 1-1 capital in their pockets because I believe that Manchester United will improve their performance in order to win at home and ensure that they qualify for the next round.
It's not all about a Ronaldo, but about how to play really well in order to win against Atletico Madrid.
They played aggressively against opponents in Premier League but they did not get good results. From the match in a first leg against Athletico Madrid, I don't see any difference from Manchester United performance. They still rely on De Gea to save their goal, rely on their stars' personal performance and moments to score goals and win or get a draw. It is not what a winning team should have.
Even Athletico Madrid have their problems which are shown with their current position in La Liga, they are still have better connection and psychology in their team. I put my belief on them in the second leg, even it will be hold in Old Trafford.
I think not really have problem between Manchester United or Atletico Madrid because both team still not safety on 4th standing position on each domestic league, I see have potential for Manchester United will qualify next round with playing home on second leg. But some time Manchester United is not always take advantage playing as home because many time loss three points when play on Old Trafford. I think second leg match of EUFA Champion League will be interested match for both team and who pass to next stage.