Having reached a record 41 goals in La Liga on Saturday, Cristiano Ronaldo will focus his scoring boots on the Champions League on Tuesday, a competition where he has notched up a mere eight goals in eight games.

And it is the performance of the Portuguese star that could be crucial to the outcome of the semi-final encounter as Real Madrid take on another giant of European soccer, Bayern Munich.

Real and Bayern have won Europe's premier club competition 13 times between them and will be meeting for the fifth time in a European Cup semi-final.

If Los Blancos are to improve on having won just one of those previous four meetings, then it is Ronaldo who could hold the key.

The 27-year-old goal machine will likely be going up against one of the best outside backs in world soccer in Philipp Lahm on Tuesday. But if Ronaldo is able to get the better of the Germany captain then Real could flourish against what is, despite statistics suggesting otherwise, a suspect Bayern defense.

Bayern have conceded a league low 20 goals in the Bundesliga this season but could be exposed against a Real side that has scored a record 107 goals in La Liga.

Not only is there Ronaldo, but also the attacking threat of Karim Benzema, Gonzalo Higuain and Mesut Ozil. And as if that weren't enough, Angel Di Maria has returned to fitness and set-up a goal after coming off the bench against Sporting Gijon at the weekend.

It is a formidable prospect, the likes of which Bayern have yet to face this season. And the Bavarians' defense looked none too impressive as they went down 1-0 to Borussia Dortmund last week in a result that has virtually assured that Bayern will fail in their bid to regain the Bundesliga title.

But if Bayern could be exposed against superior opposition, the same is also true for Real. Jose Mourinho's side have progressed comfortably to the Champions League semi-finals, with a relatively straight-forward draw.

After Lyon, Ajax and Dinamo Zagreb were disposed of in the group phase, CSKA Moscow and Apoel Nicosia were comfortably put to the sword in the knockout stages, 6-2 and 8-2 respectively.

And with the strength in depth in La Liga not the strongest, there is an argument to be made that the only top level team Real has faced this season is Barcelona. A match which Los Meringues lost 3-1 to their arch rivals at the Bernabeu in December.

Bayern may not be at Barca's level, but they are a step-up in class from what Real face week-in week-out. Certainly outside of the giants from Catalonia there is no team in Spain that can boast the attacking threat that Bayern possess in Mario Gomez, Franck Ribery, Thomas Muller and Arjen Robben.

And, while he may be the most inconsistent and frustrating of those four, it is Robben who has the ability to change the complexion of the semi-final.

Likely to be going up against the forward-bursting Marcelo, Robben has the ability to cause real damage cutting inside from the right.

Robben was superb in doing just that as he led Bayern Munich to the Champions League final and Holland to the same stage of the World Cup in 2010 and if he can replicate that form then he will cause Real untold problems. His space may be limited in the first leg at the Allianz Arena, where Mourinho will likely set-up his side more defensively, but in Madrid Robben can be a constant threat on the counter attack. In a tie as potentially close as this one, away goals could be vital.

But then again, the flying Dutchman could have another performance of the ilk he put in against Dortmund. To the condemnation of many, Robben first played Robert Lewandowski onside for Dortmund's first goal before missing a penalty and then completing a horror hat-trick by missing a gilt-edge chance late on.

He can be egotistical and as fragile as a snowflake but Robben can also decide a match with a sparkling dribble and waft of his left boot.

And surely eager, not only to atone for his horror show at the Westfalenstadion, but to put one over the club that discarded him nearly three years ago, Robben could earn his way firmly back into the hearts of all at Bayern.

First Leg Prediction: Bayern Munich 1-1 Real Madrid