Jay: That's why Pep is the best. Tried something outrageous yet was willing to concede and change when it didn't work.

Peter Collins: Great game to watch, but I bet Mourinho is having a heart attack. He loves to control games, not leave them as open as this!

lfcway: I would have put my house on Suarez and Neymar scoring those chances. How is this game still 0-0?

D'Josh Impact: What makes a great coach is the ability to learn. Pep has changed the formation recognising his own madness. RESPECT!

Join the debate and get involved via #bbcfootball, external on Twitter, 81111 on text and the BBC Sport Facebook page., external And you can place your vote on the right-hand side of this page.

An excellent first eighth of this tie. Two heavyweights going toe-to-toe. Like Creed v Balboa II.

Image source, Reuters

Change the system all you like, but you can't stop Lionel Messi. He dances between two white shirts on the corner of the box before curling one wide. Lovely feet. Compelling game...

Image source, Reuters

Image source, opta

Here's how Bayern Munich lined up in the first 15 minutes or so. Rafinha (13), Jerome Boateng (17) and Medhi Benatia (5) were a back three, but also look how high Robert Lewandowski (9) and Thomas Muller (25) were. No parking the bus here.

Gary Lineker
BBC Sport

"Even Pep has recognised his own madness and changed things."

Mark Lawrenson
Football Analyst on BBC Radio 5 live

"It almost looked like Robert Lewandowski was taken by surprise by the quality and accuracy of Thomas Muller's immediate return ball back into the six-yard box. It should be 1-1."

Rafinha has now gone from left of a back three to right-back. You keeping up with this? There will be a test after the game.

QPR midfielder Joseph Barton has tweeted:, externalTactically fascinating. They say the line between madness and genius is very close. On this evidence I have to agree. Get viewing though.

CHANGE!

There goes the change in tactics as Bayern Munich go to a back four. They had to do something.

And they instantly create a great chance! Thomas Muller beats his man on the right, whips in a cross and Robert Lewandowski is free in the middle. A clean connection on it, and he scores. He has to - but he stretches and the ball slides wide...

Andy West
European football writer

"Fascinating to see Bayern man-marking Barca literally all over the pitch. It's not really working at the moment because Barca have the individual quality to beat their men and create space."

Image source, Bayern Munich

Bayern Munich's Twitter , externalenjoyed Neuer's save from Suarez.

Grant Walker: Barcelona vs Bayern. Most open game I've seen in a while. Incredible fitness levels by both teams,

Zsolt Janos: Neuer has already had more touches than Bale yesterday.

Will Davies: 3 v 3 at the back For Bayern seems suicide at the moment. I think Pep wants this game to entertain the masses!

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Bayern Munich's 5-a-side style man-to-man coverage is boggling minds.

Neymar is close to the opener now as he scuffs an effort wide after great work from Luis Suarez. Barca will score soon if the shape of the game stays like this. It looks inevitable...

Mark Lawrenson
Football Analyst on BBC Radio 5 live

"There is just so much space. Luis Suarez must have been 20 yards clear of any Bayern Munich defender when he went through there. It was a tremendous save from Manuel Neuer to deny him."

Gary Lineker
BBC Sport

"This is so open there has to be bags of goals.....get your cash on 0-0."

Bayern have had 55% of the ball in the opening 10 minutes. Part one of the plan is working for the Germans.

But part two - keeping the Catalans out - almost falls flat as Luis Suarez has 45 yards of space to run into! He's one on one, the defence gone AWOL, but Manuel Neuer makes a brilliant Peter Schmeichel-style starfish save.

Image source, Reuters

This three-man defence will either be a touch of genius from Pep Guardiola, or a case of madness. Time will tell. Lionel Messi almost gets clear again but Bayern just about scramble it away.

Mark Lawrenson
Football Analyst on BBC Radio 5 live

"This is an absolutely intriguing game. It is far more open than I expected it to be and both sides are looking dangerous every time they come forward."

Bayern Munich are leaving three-on-three at the back and it almost comes unstuck as Lionel Messi skips past a man and finds Luis Suarez. They are two on one but Suarez takes the wrong option, shooting low at Manuel Neuer from 20 yards.

If Lionel Messi is free, it usually pays to pass it to him...