He rounded Anton Ferdinand, who had replaced the injured Robbie Stockdale after twenty-one minutes, to drill home at David James' near post.
Don Hutchison was denied an equaliser shortly after that when he played a one two with Richard Garcia, himself a substitute for Rob Lee in the second half, only for Spurs 'keeper Keller to push the shot round the post for a corner.
Lee himself could have scored in the first half when Defoe's clever chip set him up, but his left foot strike bounced off the post to go into Keller's hands.
Chances were few and far between for Defoe, who was without regular strike partner David Connelly, but he did have a one on one with Keller, only to see his shot smothered.
Richard Garcia might have covered himself in glory at the end of normal time, but he took too long and his chance, like West Ham's progress in the Carling Cup, was gone.