Discovered? He gave him his first games, certainly. In truth (I just checked) Dunk wasn't a nailed on starter under either (50 games across four seasons). He cemented his place (38 games) in the Sami / Jones / Hughton season.
March though - never made a first team appearance under Poyet (unused...
Gus didn't really trust them, tbh. Oscar Garcia did though.
Ince, Forster-Caskey, March and Dunk all played much more regularly under him, than Gus Poyet.