Carlo Ancelotti's side enjoy the slenderest of advantages over their hosts, but will be wary of his club's terrible record on German soil, per UEFA.com's Steffen Potter.
The Bavarians, and Pep Guardiola in particular, need to heed the lessons from the first leg when Bayern enjoyed the lion's share of possession but lost to the breakaway goal from one of Real's lightning-fast counter-attacks.
In truth, it should really have been more than a one-goal defeat, but perhaps just as importantly, Bayern were unable to secure the away goal.
One goal for the away side here and the entire complexion of the tie changes.
After missing the Copa del Rey final and a couple of La Liga games, the Portuguese has come back into form with all guns blazing.
Just one more goal would see Ronaldo out on his own as the all-time leading scorer in the competition's history in either format:
Currently tied on 14 goals with AC Milan's Jose Altafini and Barcelona's Lionel Messi, you can be assured that before he leaves the pitch on Tuesday night he will want to have his name written large across proceedings.
Don't be at all surprised to see balls raining in from all angles as he seeks to secure his place in the annals of history.
If Pep Guardiola looks to implement a 4-1-4-1 formation, then the role of Javi Martinez just in front of the defence is a hugely important one.
Firstly, it allows Philipp Lahm to revert to his more natural right-back role—one which will curtail Madrid's raiding down the flank, and which could've stopped the only goal of this tie from the first leg. Indeed, Jason Le Miere noted for International Business Times:
If Ronaldo is switched back to the left in a 4-3-3 the there is even more reason for Lahm to be switched back to what was his default role before this season.
His inclusion in that role would not merely be for defensive purposes. At full-back, Lahm also provides a valuable extra attacking threat.
When Guardiola finally made the change midway through the second half at the Bernabeu, Bayern had plenty of late joy down that flank with Lahm testing out a struggling Isco.
What that switch also does is allow Martinez a relatively free role in front of the back four. His movement across the line is crucial in cutting off the supply inside the full-backs, and he also offers a great aerial presence should the balls find their way into the box from the ball played in.
Boundless energy will also see him join the attacks as much as possible with Xabi Alonso charting Martinez's late runs, the Madrid centre of defence is particularly exposed to the cut and thrust of Bayern's attack.
Per WhoScored.com, Bayern are undefeated against Real in their last eight home matches in all competitions.
Of more concern might be Real Madrid's form in Germany generally. Two wins in 26 matches on German soil, per UEFA, is unbelievably poor for a club of Real's stature.
Real have won six of their last seven in the Champions League, per WhoScored, and in Cristiano Ronaldo they have the top scorer in the competition.
In Toni Kroos and Philipp Lahm, Bayern have two of the top four passers in the competition. Per UEFA, Kroos has completed an astonishing 948 passes from 1,070 with an accuracy of 89 percent.
Lahm fares only slightly worse, 807 completed passes from 908 attempted, again with an 89 percent accuracy.
This match is perfectly poised. Carlo Ancelotti has already stated that his team will start quickly, per Nesha Starcevic of the Associated Press (via The State), and an early goal will put Real on the front foot and in control of this tie.
Control is something that Pep Guardiola clearly enjoys and probably expects from most of the games his Bayern side play, but control with no incision is moribund.
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