 In 2010, O'Brien was again nominated for the Associate and Affiliate Player of the Year Award, this time alongside two other Ireland players (there were 16 nominees in all); the award was given to Netherlands Ryan ten Doeschate.O'Brien was selected in Ireland's 15-man squad for the 2011 World Cup hosted by Bangladesh, India, and Sri Lanka.On 2 March O'Brien hit the fastest century in World Cup history, off just 50 balls against England helping his team to successfully chase down a target of 328 when at one stage they were struggling at 111/5.