minor league vs minors

minor league and minors both are nouns.

Word	Noun	Adjective	Verb	Adverb
minor league	Yes	No	No	No
minors	Yes	No	No	No

As nouns, minor league and minors are synonyms defined as:

minor league and minors: a league of teams that do not belong to a major league (especially baseball)

Other synonyms of minor league include bush league.

minor league (noun)	minors (noun)
a league of teams that do not belong to a major league (especially baseball)	a league of teams that do not belong to a major league (especially baseball)