The 21 year old, who cost the Millers £65k last season as a replacement for Will Hoskins who departed to Watford added, "There's little bits and bobs that he's already tried to drill into me, like heading, to be in the box at every opportunity when a cross comes in and make sure you're there, which maybe I didn't do so much before."
O'Grady scored 4 goals from 11 games last season after joining in January.