...
I shouldn't continue.
But I will, because I am bad, and stupid, and make bad life choices. Firstly, none of those vaults were about a simple, 'he loses possession too much'. Which is a fair (if a bit harsh) criticism. They were prefering Oviedo over Del, because all Del can do is 'run fast'. Which was madness, even then.
Secondly, he's a tricky winger that needs to try stuff. He'll fail most of the time, but make magic the 1-2 times he doesn't. As he should generally be far up the pitch when attempting that stuff, it's not a huge drawback, and there is huge benefit in it. In other words, of course he loses the ball. You tend to lose the ball sometimes when you actually try to do something with it. Look at the players that don't lose the ball - McCarthy, Barry, Cleverly. The players that do - Del, Mirallas, Rom. Their roles have quite a bit to do with it. And the players with magic in their boots will still lose the ball sometimes.
That's not to say Del is the complete player, nor to say he's the finished product. But you must be on a windup to question his brilliance overall.
