save vs make unnecessary

save is a noun but make unnecessary is not a noun.

Word	Noun	Adjective	Verb	Adverb
save	Yes	No	Yes	No
make unnecessary	No	No	Yes	No

As verbs, save and make unnecessary are synonyms defined as:

save (noun)	make unnecessary (noun)
(sports) the act of preventing the opposition from scoring

save (verb)	make unnecessary (verb)
make unnecessary an expenditure or effort	make unnecessary an expenditure or effort
record data on a computer
to keep up and reserve for personal or special use
accumulate money for future use
spend less; buy at a reduced price
retain rights to
spend sparingly, avoid the waste of
bring into safety
save from ruin, destruction, or harm
save from sins
refrain from harming