When Saul saw David go forth against the Philistine, he said to Abner, the captain of the host, Abner, whose son is this youth? Abner said, As your soul lives, O king, I can't tell.
"When Saul saw David go down against the Philistine"  (1 Samuel 17:54). This should read, "When Saul had seen David go down against the Philistine."  Saul would not have inquired about David until after his victory.