Warnapura was the 11th Sri Lankan ODI cricket cap. His One Day International (ODI) debut was against West Indies on 7 June 1975, in a 1975 Cricket World Cup match that was also Sri Lanka's first ODI. He was dismissed for 8 runs in that match, which Sri Lanka lost. He was given the captaincy of the team to temporarily replace Anura Tennekoon (who was injured) in his fifth match, which was played against India on 16 June 1979, as part of the 1979 Cricket World Cup. He led the team to victory, scoring 18 runs in the match and taking a wicket. It was also the only victory in the series by an Associate Member nation (Sri Lanka had not yet gained Full Member status) in the tournament.