 Born in Colchester, Essex, Pentney started his career with the Leicester City youth system, where he was a regular for the under-18 side as well as the England under-17 team.He was part of the under-18 squad that won the FA Premier Academy League by beating Sunderland under-18s 4–3 in a penalty shootout in the 2006–07 season.Pentney signed his first professional contract on 5 May 2007, signing a one-year deal alongside Andy King, Max Gradel and Eric Odhiambo.