pitcher vs baseball player

pitcher and baseball player both are nouns.

Word	Noun	Adjective	Verb	Adverb
pitcher	Yes	No	No	No
baseball player	Yes	No	No	No

As nouns, baseball player is a hypernym of pitcher; that is, baseball player is a word with a broader meaning than pitcher:

Other hypernyms of pitcher include ballplayer, thrower.

pitcher (noun)	baseball player (noun)
the position on a baseball team of the player who throws the ball for a batter to try to hit	an athlete who plays baseball
an open vessel with a handle and a spout for pouring
(baseball) the person who does the pitching
(botany) a leaf that is modified in such a way as to resemble a pitcher or ewer
the quantity contained in a pitcher