A worthy opponent enhances our own worthiness.In many aspects of life, we are always in a group with similar goals and targets but limited rewards or prizes.
If a rank holder in a class is a good-natured student, he or she would be imitated by a handful of other students and they would certainly perform better than before. If an athlete who is the anchor of a team and also becomes a match-winner, other try to emulate him or her and naturally improve their performance also.
An honest vegetable vendor who is popular in the market to whom people always flock to would inspire other vendors also to reach his standards and indirectly improve their image too. This can be similarly applied in an office, in politics, between industries and even nations.
But if the opponent is unworthy, then they would or would have resorted to unfair means to stay in the picture. At such times, it is better to back off rather than trying to imitate an unworthy opponent because we may also become unworthy.