sad sack vs fumbler

sad sack and fumbler both are nouns.

Word	Noun	Adjective	Verb	Adverb
sad sack	Yes	No	No	No
fumbler	Yes	No	No	No

As nouns, sad sack and fumbler are synonyms defined as:

sad sack and fumbler: someone who makes mistakes because of incompetence

Other synonyms of sad sack include blunderer, botcher, bumbler, bungler, butcher, fuckup, stumbler.

sad sack (noun)	fumbler (noun)
someone who makes mistakes because of incompetence	someone who makes mistakes because of incompetence