This proverb implies the existence of at least two blades. Leaving one blade alone, both blades remain blunt and useless. When interacting with each other, both are sharp and helpful. So athletes are not exempt from that. On the contrary, all the beauty of this proverb is noticed in sports.
The athlete “sharpens” and develops his skill, precisely through his opponent or through his team player. Without them he would not be a successful athlete, nor would he be a record breaker. There were no victories because there would be no one to win.
Victory is overcoming obstacles, whether it is an external result, which can materialize in victory or in achieving personal satisfaction.