Even a team like Barcelona lines up with Busquets and Rakitic as their defensive cover in midfield. Real Madrid has Kroos and Modric, and sometimes Casemiro. I really don't think you can line up with 5 attacking midfielders unless you are playing a third or fourth division team in a cup game or maybe a semi-pro team in preseason. If its international football, maybe against a team like Lichtenstein or Andorra.
There's a reason Busquets is always in Barca's starting 11. Why Casemiro's in starting 11 in Real since Zidane took over.
To be fair, I think all the CMs in Barca and Real (measuring sticks for excellence at this point) are defensively very capable. Modric, Iniesta, Rakitic and Kroos all play a responsible defensive game and all of them are model CMs.
But even so, their coaches prefer to have a proper DM on the pitch with them, and that's been the way they have been successful.
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As for the teams, it's very hard to tell... Forwards are likely a wash, difference being that Messi's team wouldn't have a natural striker/finisher, even though they would likely be able to create more further down the pitch.
OTOH, Ronaldo and Suarez have more finishing power, but would likely get less service than Messi's trio up top.
Defense is sort of a wash, Neuer wins over anyone in goal.
Midfield's the most interesting one.
Kroos and Pogba playing behind James makes sense, except that James is still to prove he's a top player on a consistant basis at club level.
Modric and Iniesta would likely be the world's best CM duo, but I don't think Müller's stye fits playing with Ronaldo and Suarez at all. He's more of a finisher, runs into empty pockets, into space... This team would benefit a lot more from someone like Özil in Müller's place.
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What I'm saying is... Both teams are absolutely loaded with star power, but I do wonder if the chemistry would be there.