Real Madrid's match with the Red Devils in the Champions League this Tuesday marks the Portuguese winger's first match in the Theatre of Dreams since leaving United after the 2008/09 season.
Ronaldo was one of the best players in the world before moving from the Santiago Bernabeu. In the four seasons since, he's still managed to take a Herculean leap in his career, scoring 136 goals in 126 La Liga matches and 30 goals in 35 Champions League matches.
This season has been no different. Despite Madrid's rather pedestrian—at least by their standards—league campaign, Ronaldo has been the engine for Los Blancos' attack and maintained his insanely high level of production.
February's 1-1 draw could be considered a bit of a letdown for Real Madrid as that away goal could prove crucial for the Red Devils. With quite a bit of pressure on, Ronaldo will be the one to step up and carry Los Blancos on to victory.
The Red Devils are in a bit of a tricky position. That away goal is a nice comfort, but it doesn't offer all that much security. United can't afford to simply sit back for most of the match and let Madrid come at them. The club will need at least another goal if it has any hope of getting to the next round.
That strategy has worked this year against Madrid, but the Champions League is a much different beast from La Liga play.
On the other hand, Sir Alex Ferguson also can't afford to simply throw attackers forward because Madrid is arguably the best counter-attacking team in the world. With the speed Los Blancos have, they can turn almost any move from defense to attack in a heartbeat.
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It's on the counter that Ronaldo will be his most effective. He's one of the fastest players in the world and will be able to exploit whatever space is given to him.
There are so many ways that Ronaldo can score that you can try almost every way to stop him, and it still won't work. His headed goal against United in the first leg two weeks ago was magnificent. It just illustrated the freakish athletic ability of Ronaldo and how skilled a header he is.
Playing in Old Trafford again might bring up some good memories and make Ronaldo a bit emotional, but it's not going to hold back his play on the pitch. If anything, it could provide the kind of impetus needed for the winger to take this tie over.
Rafael has been a very good right-back at times, yet has also shown some signs of letting the match get away from him and losing his head. Regardless of the Brazilian's ability, there isn't a single defender on the planet who can stop Ronaldo. Ferguson will have to deploy either Phil Jones or Michael Carrick as cover to help defend.
In the end, it won't be enough as Ronaldo is simply too skilled to be reigned in.