3 takeaways from Madrid's manic triumph over beleaguered Bayern

No one could ask for more from Tuesday's exhilarating, emotional, and maddening Champions League quarter-final second leg in the Spanish capital. Real Madrid and Bayern Munich exchanged blows in an open game that featured every kind of goal - beautiful and erroneous - and combined for 51 shots.

Madrid ran away with the contest in the end, claiming a 4-2 win on the night and 6-3 victory on aggregate after a three-goal burst in extra time.

There were several controversial calls as well. Bayern was forced to play with 10 men in the final 37 minutes after a dubious red card to Arturo Vidal, and two of Cristiano Ronaldo's goals appeared to be offside.

But before all that, these two European giants slugged it out and gave neutrals every reason to be entertained.

Here are three takeaways from an exciting two hours in Madrid:

Officials ruin evenly poised match

Let's get this one out of the way: Match referee Viktor Kassai and his linesmen completely ruined what was a fantastic spectacle at the Santiago Bernabeu.

Firstly, Kassai neglected to give Casemiro his marching orders for a deliberately late challenge on Arjen Robben in the 80th minute, and just 180 seconds later, the Hungarian official opted to send off Vidal for a tackle he won cleanly on Marco Asensio.

Despite the unfavourable decisions, Bayern continued to attack and make the occasion competitive.

The visitor, however, was punished again in extra time.

Ronaldo was offside before scoring his second goal of the night, and the Portuguese superstar appeared to stray offside again before clinching his record-breaking hat-trick.

Related - Look: Ronaldo puts Real Madrid into semis with 2 offside goals

The last thing Madrid needed was an excuse to win this game, or an asterisk beside the score card, because it could have won without any outside assistance. Both sides had been playing breathless football before these controversial incidents, Madrid taking a foothold in the first half and Bayern responding with delightful verve.

FIFA and the International Football Association Board have taken steps to introduce Video Assistant Referees, dry-testing technology in the Bundesliga and Major League Soccer, but UEFA president Aleksander Ceferin has said UEFA currently has no plans to implement it.

Nights like these force us to ask why the world's most popular sport - not to mention one of the most lucrative competitions - has yet to join the 21st Century. Calls that inspire hours of post-match shouting and groaning could be overturned in real time within just a couple of minutes.

"In (the) future I hope the referee is helped by TV," Ancelotti said, according to The Associated Press' Ciaran Fahey. "Because it cannot be you have these mistakes in the Champions League quarter-finals."

Robben's wing play gives Bayern life

Bayern only had a chance because of Robben, who, unlike his no-show in the first leg, charged at Madrid with purpose and disrupted its balance. The Dutchman's enterprising play led directly to Zinedine Zidane's two substitutions in the second half - Asensio for Karim Benzema and Lucas Vazquez for Isco - as the stoic Frenchman gave more support to his full-backs.

Robben simply had a monstrous impact in the second half. Minutes after seeing his wicked shot cleared off the goal line by Marcelo, the 33-year-old drew the penalty - which was also dubious - that Robert Lewandowski converted for Bayern's first goal. Robben also delivered several balls behind the defence, some of them just a touch or two from being goals.

He constantly probed Madrid for openings, and had Zidane not scrapped a midfield diamond for a wider shape, Bayern could well have scored the necessary goals to avoid extra time and win on aggregate.

For large parts of the game, Robben was able to contain Marcelo and keep him from making dynamic runs and breaking into midfield. The more possession Bayern had, the more of it went through Robben, and the more Marcelo had to stay back.

That changed in extra time as Bayern struggled to keep up, and Marcelo proceeded to gallop all over its tired midfield.

Ronaldo makes history again

Even if Ronaldo benefitted from two offside goals, the 32-year-old proved he can offer Madrid and Zidane just as much from a central position as he can from the wing. He scored via header, left foot, and right foot to complete a perfect hat-trick.

But it was his overall movement as a No. 9 that should impress the Bernabeu faithful and give Zidane and club president Florentino Perez evidence that Ronaldo can eventually move into the middle as he approaches the final years of his career.

Once Benzema departed, Ronaldo was the one who gave the recently injured Mats Hummels and Jerome Boateng a headache. They were exposed. It's not so easy to defend against Ronaldo because he's not a static presence - only 12 of his 47 touches came inside the penalty area - but when he does arrive in the 18-yard box, he makes it count.