Fantastic post Juan.
I would possibly only disagree with some of the Mascherano comments.
He has become a world class player through having a tremendous engine, being a brilliant tackler, retaining possession well and being able to spread the play, not to mention his passion. He has not built his reputation and become Argentina's captain on being a playmaker, or being the focal point of a midfield. He has always had players for club and country alongside him who have been the inventive passers, for me him and Alonso were the perfect match and the best central midfield pairing around.
I think both him and Lucas could be ideal foils for a midfielder with a bigger passing range, albeit in different ways. I fully expect Masch to be the foil for Aquilani when he is fit, with Lucas coming in when Rafa deems necessary.
I think over the past 5 years we've got so used to seeing Alonso run a midfield the way he does that we sometimes forget there's more than one way to skin a cat. Don't get me wrong, I absolutely adore midfielders like Alonso who could run an entire game without ever leaving the centre circle, but there's other ways to dominate a midfield.
Mascherano may not be as talented as Alonso, but some times presence makes up for talent. If it was purely down to talent the Roy Keane probably wouldn't have been playing at Manchester United. He wasn't a bad footballer, but in terms of ability on it's own he never should have been at that level. He had an aura about him though, which is what Mascherano needs to develop.
He's a better footballer than sometimes given credit for. He's not going to make Alonso feel embaressed, but he can ping the ball about when he wants to (played a great ball for Insua against Stoke the other week) and he can also go on those driving runs with the ball (like he did in the build up to Babel's winner against the mancs last year). He just doesn't do it enough. He's quite content to just move the play on to the next bloke and so is Lucas. Mascherano is now at the point in his career where if the play is going sideways he should be able to step forward with the ball and make something happen himself. He's not going to beat five players and curl one in from 20 yards, but he's more than capable of drawing 2 or 3 opponents toward him which will leave someone else in space.
He's coming up to the age now where he should be running midfields, not just being the silent assassin that stops others from doing it. I think he's got the ability to as well. Again, he's not Xabi, but he doesn't need to be. You can change the tempo of a game by just running at a guy with a bit of purpose - Mascherano can do that. He's at the point in his career where it's time to take his game beyond just winning the ball back at playing it simple. That's all that's needed maybe 90% of the time, but occasionally he needs to just step up the tempo of a game and take it on himself to drive the team forward and show a bit of intent.