I know tons of guys who play mostly futsal (dunno what's that in english) with the same or better skills than messi. the reason they never make it to field soccer is because they lack the physique.
Not really. Football and Futsal are closely related, but different sports. Many skills that are applicable in football are the same ones that are applicable in futsal. The thing is, futsal is less physical and lasts much shorter. Football requires much better cardio (more than twice as long) and durability (more people trying to rough you up and given more freedom to), but the actual ball control skills are the same. Field hockey and Floorball are variations on the same sport, and the same goes for Football and Futsal. Or Arena Football and NFL. That would be a more valid comparison. Guys can go from Arena Football to the NFL if they have the ability (Tommy Maddox, for example, spent a while in AFL before returning to the top level, and more famously Kurt Warner got his break there after going undrafted), but the NFL is much bigger, more challenging, and features more physicality. Only a few Arena Football players can make it on the NFL stage, but there are plenty who can cut through tiny gaps, have all the jukes, jives, spins and all the pace to make it, take great catches, kick extremely accurately.
The futsal guys may be able to pull off the same tricks as Lionel Messi. Some of them may be able to pull off even more impressive ones. But Lionel Messi does it after 89 minutes of running harder and faster against people who can be more physical against him, and that is the real difference.