DID SAUL KNOW WHO DAVID WAS?

I Samuel 16:21-22  And David came to Saul, and stood before him: and he loved him greatly; and he became his armourbearer.  And Saul sent to Jesse, saying, Let David, I pray thee, stand before me; for he hath found favour in my sight. (KJV) I Samuel 17:57-58  And as David returned from the slaughter of the Philistine, Abner took him, and brought him before Saul with the head of the Philistine in his hand.  And Saul said to him, Whose son art thou, thou young man? And David answered, I am the son of thy servant Jesse the Bethlehemite. (KJV)

Note: The assumption of contradiction here is that if Saul and David met in chapter 16 and made such a great impression on each other, wouldn't Saul have recognized David in chapter 17? However, the context of the later meeting makes it quite likely that Saul would not recognize David.  The last time he had seen David, David was a simple musician.  Suddenly, some time later, David was a great warrior who had just slain Goliath.  Saul would not recognize David, since he never thought of David as such a valiant person.  Not a contradiction.