A premixer for a combustor includes: a centerbody having a hollow interior cavity; a swirler assembly radially outward of the centerbody; a peripheral wall disposed radially outward of the centerbody and the swirler assembly such that a mixing duct is defined between the peripheral wall and the centerbody, downstream from the swirler assembly; an annular splitter radially inward of the swirler assembly and radially outward of the centerbody such that a radial gap is defined between the splitter and an outer surface of the centerbody, wherein the splitter includes a trailing edge which extends axially aft of the swirler assembly; a fuel gallery disposed inside the interior cavity of the centerbody; and at least one fuel injector extending outward from the fuel gallery and passing through an injector port communicating with the outer surface of the splitter.