Sanchez has amazing potential to succeed because he's got it all. It will take a great coach to get the best out of Sanchez, though.
He was very good for Chile (overtrying things a bit, but he was excellent in doing his duties up and down his side) and he was very good for Udinese in the later part of the season. The rest of his Udinese period? Hot and cold, much more cold, and we're talking 2 seasons.
The worrying part is that he was not only terribly inconsistent, but he also didn't look motivated. Is he playing only when it counts? To make the WC squad or to make an impression on the potential buyers?
Dunno. But he's only 21 and flaws can easily be eliminated with the right person working with him.