player vs walk-on

player and walk-on both are nouns.

Word	Noun	Adjective	Verb	Adverb
player	Yes	No	No	No
walk-on	Yes	Yes	No	No

As nouns, walk-on is a hyponym of player; that is, walk-on is a word with a more specific, narrower meaning than player:

player (noun)	walk-on (noun)
a theatrical performer	plays a small part in a dramatic production
a person who participates in or is skilled at some game
someone who plays a music as a profession
a person who pursues a number of different social and sexual partners simultaneously
someone who takes part in an activity

player (adjective)	walk-on (adjective)
	not capable of or especially not involving speech or spoken lines