Your statistics are, to be kind, slightly skewed. His job, when he gets to the byline, is to put the ball into dangerous areas where either players are, or where they can run onto the ball. He does neither on a regular basis, and his statistics prove it. He hits far more first defenders than anything else, but is the consummate corner winner...if that is considered a plus!
One of the things that disturbs most is that he never seems comfortable on the ball. It seems like it is a hot potato to him. In a team where he is surrounded by players who are almost nonchalant in their possession of the ball, his frenetic actions smack of a lack of confidence, ability and quality.
Yes, I will grant you he has speed to burn. However, when was the last time we had a fast break in which Navas had a telling part....other than the one at Palace where De Bruyne sent him away, he rounded the keeper and then fluffed his lines, of course?! Did I mention, frenetic?!
Seems to me that an attacking midfield of KDB, RS and DS is going to play every game they are fit. The quality of their passing, the weight of their passes, their movement off the ball, etc, etc, etc, are all far superior and, if we need someone to get in around the back I'm not even sure Navas is your man then. I expect he will be gone by Sept 1, 2016, as his quality is not on a par with the players around him, and he is certainly not better than the new players brought in. With Barker and Roberts looking for a place on the bench, he may be a makeweight in the not too distant future.