The Bavarians are 2-1 down after defeat at Allianz Arena and are up against it to secure passage, with Madrid likely to turn up the temperature at Santiago Bernabeu on Tuesday.
But there are strategic considerations for both sides and with that in mind, we examine some of the key tactics for Zinedine Zidane and Jupp Heynckes.
ATTACK THE FULL-BACKS
It’s an obvious area for exploitation but if Bayern are to regain control, avenues out wide will provide a route back into the tie.
The Jekyll-and-Hyde nature of Marcelo was on full display in Munich, his attacking talent in grabbing the equaliser arriving after his negligent positioning for the opener – he was virtually off the pitch as Joshua Kimmich burst into open grass.
The Brazil left-back can be so high up the pitch at times he’s often closer to the opposition box than his own when the ball breaks. In the absences of Kingsley Coman and Arjen Robben, Thomas Muller’s craft on the right-side for Bayern could prove profitable.
But like crossing a T junction, it’s not just right but left which needs attention.
Dani Carvajal is absent for Real after limping out for the first-leg and Lucas Vazquez will likely drop in to replace his Spanish counterpart as he did towards the end in Munich.
While he is versatile, Franck Ribery will look to isolate him one v one from the off and that prospect should have the veteran Frenchman licking his lips.
Cristiano Ronaldo is the Champions League’s finest goalscorer and with 15 goals in the competition so far this season, his pedigree is clear.
However, in Germany the 33-year-old was shackled in the spearhead of Zidane’s disjointed 4-1-4-1.
The tactic to sit back, soak up pressure and spring their attacks on the counter relied heavily upon the performance of Isco to provide the ingenuity for his intelligently angled runs.
But the Spain playmaker was poor, Madrid ended up running into traffic through the middle and it took the appearance of Marco Asensio from the bench in a wider berth on the left to really make it an effective away-day performance.
In Madrid, while Zidane knows Bayern require two goals at least, the rollicking Juventus comeback in the quarter-finals is a warning to kill the tie off early.
Ronaldo needs a partner alongside him and either Asensio, Karim Benzema or Gareth Bale must be brought into the XI to occupy some of the visitor’s attentions.
This is a note for both. Madrid have shown repeatedly this season they are fallible from a decent delivery, whether it be from the wide areas or a set-piece.
Keylor Navas’ propensity to punch rather than gather can breed a little insecurity, while the full-backs – it always seems to be Carvajal – are often left in lopsided one-v-one aerial battles.
James Rodriguez has a heat-seeking left-foot and although the likes of Muller and Robert Lewandowski froze in front of goal last week, they could be prime targets for the Colombia playmaker in the Spanish capital.
Equally, Toni Kroos is one of the best deadball specialists in world football, from wide free-kick positions of course with Ronaldo taking the responsibility with a sight of goal, and on either corner.
Three of the German’s six La Liga assists this season have been conjured from corners and his ability to blend pace, height and spin makes for a devilishly difficult delivery to defend.
Ronaldo, Sergio Ramos and perhaps even Bale are all proven aerial goalscorers and if Real are looking to kill the tie off, set-pieces could be the way through the German wall.
Both sides were hit by injuries in last week’s clash at Allianz Arena. Arjen Robben and Jerome Boateng will both miss the second leg for Bayern, while Dani Carvajal and Isco are absent for the hosts.
With enforced changes to both starting XI’s, new protagonists could rise to the stage, so we take a look and compare players in positions we think will be crucial.
MARCO ASENSIO V JAMES RODRIGUEZ
James Rodriguez can expect a warm reception as he returns to Santiago Bernabeu for the first time since his summer departure.
If he produces a performance akin to his showing in the Allianz last Wednesday, however, the home fans will turn decidedly bitter.
The Colombia playmaker was Bayern’s stand-out star in the first-leg defeat, buzzing around the pitch with vigor and verve.
On the backfoot, he was positionally mature, diving into to make a Munich joint-high of four tackles while in attack his four key passes was the most in the game.
The 26-year-old has little to prove having enjoyed a career renaissance on loan at Bayern, but there will no doubt be extra zip in his step.
Another key performer in Munich was substitute Asensio. The Spain international forms part of the reason why James was allowed to leave Madrid on loan, with his emergence handing Zidane another lethal weapon.
He could well mirror James and operate as a No10 in behind a Real front two and as he showed in delicately delivering the winner last week, his left-foot is capable of inflicting damage.
Beyond his finishing ability, Asensio’s pace, particularly as Madrid will sit back and counter, is a vital asset.
The 22-year-old gives Real much-more cutting edge and remarkably since the start of last he has scored against Barcelona (two), Bayern (two), Juventus (one), Sevilla (two) and Valencia (two).
He’s a big-game player and they don’t come much bigger than this.
LUCAS VAZQUEZ V JOSHUA KIMMICH
Cover in defence has been an issue all season for Madrid.
Casemiro has dropped in at centre-back, Nacho’s operated in practically every backline position while teenager Achraf Hakimi has endured a baptism of fire in his first senior season.
So when right-back Dani Carvajal was forced off last week, it was a case of not again for Zinedine Zidane.
Vazquez dutifully dropped in to fill the void and is likely to continue in the position at the Bernabeu.
The 26-year-old (no, he is not a promising young star as commentators frequently blinded by his boyish looks note) will have his hands full as the 35-year-old Franck Ribery was a real danger in Munich.
Much of Bayern’s attacks are likely to be focused on Real’s right as they aim to exploit the perceived weakness, but Vazquez has been a trusted servant for Zidane this season.
But while right-back could be a frailty for Real, the opposite is true for the German giants.
Kimmich blasted in the opener last week and with Madrid left-back Marcelo’s slack nature from a defensive perspective, he would be afforded more opportunities in the Spanish capital.
He’s already plundered three times and added a further three assists in the Champions League this term – absurd numbers for a full-back – and if the Philip-Lahm reincarnate can break free to take advantage of the space again, Bayern will be right in the tie.
CRISTIANO RONALDO V ROBERT LEWANDOWSKI
Ronaldo and Lewandowski are the two figureheads of their respective sides but both were equally poor in the first leg.
The Poland striker has been lethal this season, scoring 39 goals, but he missed a couple of opportunities last week he would usually gobble up with ease.
He spurned a clear chance with a tame header straight at Keylor Navas and was largely anonymous throughout.
If this was his big audition to earn a summer switch to Real, he bombed it. The 29-year-old will be desperate to make amends, and having scored six times against Madrid in the Champions League – the top scorer against Los Blancos in the competition – history is on his side.
Talking of history, Ronaldo is creating plenty of it this season.
His 152nd Champions League game on Tuesday will see him set a record for the most appearances by an outfield player in the competition – only Iker Casillas (167) has played more.
The Portuguese is also the tournament’s highest scorer with 117 goals plundered and ever the ultimate competitor, he’ll want to make amends for last week’s no-show.
A victim of Zidane’s 4-1-4-1 starting shape in Munich, the 33-year-old was left painfully isolated and registered the same number of touches as half-time sub Asensio.
He can expect significantly more support with Gareth Bale rumoured to be starting on Tuesday.
The playmaker, who injured his shoulder during the first leg victory at the Allianz Arena last week, was initially set to be ruled out for up to three weeks but has miraculously proven his fitness to Zinedine Zidane and his coaching staff.
Whilst his upper upper sprain has not fully healed, Los Blancos might be prepared to take a gamble on the midfielder for such a big match after he came through a light training session on Monday.
The German giants would have been preparing to face a Whites team without the 26-year-old.
— Real Madrid C.F.🇺🇸🇬🇧 (@realmadriden) April 30, 2018