I did a small amount of research and found the two key words are dedication and determination. I also discovered that in the Bible, the word champion is only mentioned in I Samuel chapter 17 (KJV), and it refers to the enemy of the Israelite people. The enemy's name was Goliath. The Bible does not give his credentials to verify his boast, so he was only a champion in his words.
The ulitimate champion made no bragging statements, his bragging rights were just accomplishing the job given him. He was a Shepard, a keeper of the sheep. When the lion and the bear came, he simply protected the flock. In doing so, the lion and the bear were killed. The Shepard's Dad asked him to check on his brothers and in doing so, he found his brothers, as well as others full of fear. In my thinking, David did not want to go back to his Dad to tell him he left and his brothers were in a fearful state of mind. He saw what needed to be done and he did it. The Bible never calls him a champion, but other than a few indescretions, he was a champion. He completed the opportunities given to him.