Defoe, who has now fluffed four of his last five attempts, was taken off penalty duty in January - and it is unlikely he will be given the job again.
Redknapp said: "Jermain takes them in training and rattles them into the corners.
"I was hoping he'd score and I was happy with him taking it. Gareth took one and missed. Crouchy, not really. Aaron, no.
"Where do you find a penalty taker? It might be an idea for the ref just to give a goal-kick.
"You could do with someone just smashing it down the middle, putting their boot behind it."