Rafael might just have to play a perfect game tonight if Manchester United are to reach the Champions League quarter-finals. Trying to keep Cristiano Ronaldo quiet is the biggest test you can get as a right-back.
Even if you forget the physical task that awaits the Brazilian, mentally it is also a huge challenge in what is an extremely high-pressure game. There is a major onus on him to perform for Manchester United after having a tough time of things in the first leg in Madrid.
I think if Rafael v Ronaldo comes down to pace and power, then there is only one winner. The one thing Rafael must not do is allow space in behind him, or be left one-on-one, because if Ronaldo gets on your shoulder then you have big, big problems. Rafael needs to make sure that he always has Ronaldo and the ball in front of him so he knows what he is dealing with.
It is a very difficult task for the young man and he struggled in the first leg at the Bernabeu, particularly in the first half. As such, Ronaldo might fancy his chances again, but Rafael has shown more maturity in his defending this season, which is encouraging for United.
Rafael's temperament has been questioned in the past but I think it is less of a concern now. Still, we will find out tonight if he is ready to cope with the occasion. There will be so much pressure on him and he needs to keep his mind right, know when to drop off and when to go forward. He has to keep shape.
If he finds himself one-on-one he has to remember not to dive in and let Ronaldo do his tricks. If you dive in against Ronaldo he will go past you; if you stand him still, he has a problem. Ashley Cole has been the master of this in the past - he let him stand still and do all his step-overs, but the ball wasn't moving.
Challenging Ronaldo to beat him, rather than diving in rashly, is the key for Rafael. If he can keep his composure in the first five or 10 minutes and come out with the ball, then he could settle in quickly and have a good evening.
You have to team up on a player like Ronaldo and be on him as soon as he gets the ball on his feet; you need to prevent him from running straight at the defenders. Rafael will need help from the defenders to his side and the midfielders just in front of him. He needs to be aware of where Ronaldo is at all times, because Madrid will certainly know where to look for him when they are looking to break quickly.
If you are even five yards out of position, you will have a big, big problem.
Rafael will be marking Ronaldo from the start, but Madrid might feel that Patrice Evra is vulnerable, as he lacks pace now and too many players have gone around him too easily this season, but another important point is that United's defending as a unit has improved immeasurably since the return to fitness of Nemanja Vidic. He has made a big difference in terms of organisation.
We saw from the amount of goals that United let in in the first half of the season that they missed Vidic, but his return has stemmed the flow of goals conceded.
Ronaldo is one of those players, with his arrogance - and I mean that in a good way - he is going to want to prove to everyone at Old Trafford how he has become a better player since leaving the club. I don't there are many players who have departed United and improved, but he has - both as a player and as a man. He has matured.
He will want to prove his point by scoring a goal. Some players are inhibited when they return to former clubs and shy away a bit - that won't be Ronaldo tonight. A lot of United fans want to see how he has developed since 2009 and he will be keen to show them.