Ah but messi always drops behind David Villa making forward runs, so having messi 'heading' the attack isn't the way they do play it, for a replicate tactic
I had the same problem, but then i brought Messi inside, AMCR Advanced Playmaker Attack, with no right winger, pushing alves as a wingback.
With the freedom for messi he sits more inside than to the wing anyway, always running along the defence looking for his gap, or going through them. Alves then brings up the width on that side, allowing messi to roam inside on his stronger foot, and if somehow forced wide, he has the option of alves. This also holds the opposition LB in position, not letting him track messi and backup the central defenders.
The biggest task i had was getting Xavi's passes up, as i said.
I also use a different shape to your tactic, as i don't buy that barcelona play a 4-5-1 formation. Having both LB and WBR push forward, the barcelona def mid tends to drop into a third central defender position, something else i have tried replicating, and although they don't actually sit at the same level in the match graphics, i think i have the idea worked out.
I must say i'm very impressed with the way you've got Xavi working, and the goals, i never could get that balance for sure!
I think i'm going to try and integrate your passing in my tactical shape, see what I come up with. Unless you have objections?
Nice tactic!
Oh and for those on about the high possession every match, barcelona have an average of 68% possession over the last 5 seasons, arsenal are second with 65%, but are much less effective!