Whittaker hoping win will open world-title door

World title contender Ben Whittaker says all he can do is "keep knocking on the door and hopefully it will open" in his bid to secure a shot at the IBF light-heavyweight crown.The 29-year-old from Wolverhampton takes on Conor Wallace at the Utilita Arena in Birmingham on Saturday in a final eliminator for a potential fight with Russia's three-belt champion Dmitry Bivol.Undefeated Whittaker, who won a silver medal at the delayed Olympic Games in…