Messi basically played CM for much of the QFs against Belgium. Against the Netherlands, for 60 odd minutes, there was a huge bus in front of the Argentinean attack, with Messi playing as a CAM behind the three attackers. He's the walking reason why Argentina were in the game for 120 mins. Netherlands were more worried about Messi than scoring a goal themselves.
Germany, in the Final, won't park the bus. Schweini and Khedira will be after Messi all game long, but it may just be the perfect game for Messi. Unlike Switzerland and Netherlands, Germany won't entirely focus on Messi and unlike Belgium, they won't be clueless. It has all the ingredients for a classic and it's the exact kind of environment Messi excels in. For all the praise Germany is getting, their defense isn't great. Ask SchGoo, what he feels. Germany haven't been tested defensively, which doesn't bode well for them entering the Final against Argentina amidst 50,000 Argentinians at the Maracana.