Mets star Edwin Diaz won't be on a mound this season, but that doesn't mean he won't still be looking fly -- TMZ Sports has learned he's just copped a sweet new necklace ... that's worth a quarter of a million dollars!!
The closer -- who's currently on New York's injured list after tearing up his knee during the World Baseball Classic back in March -- hit up Victor Rodriguez, aka Tajia Diamonds, for the piece recently .