player vs standby

player and standby both are nouns.

Word	Noun	Adjective	Verb	Adverb
player	Yes	No	No	No
standby	Yes	Yes	No	No

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

player (noun)	standby (noun)
a theatrical performer	something that can be relied on when needed
a person who participates in or is skilled at some game	an actor able to replace a regular performer when required
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)	standby (adjective)
	ready for emergency use