The striker did so twice last night and helped to make another as Tottenham overcame a spirited Stevenage side to set up a home quarter-final against Bolton Wanderers.
Spurs certainly felt the benefit of rotation, as Redknapp made nine changes to the team which lost 3-1 to Manchester United here on Sunday. Both of Defoe's goals, the first with his left foot, the second with his right, were created by Gareth Bale, returning after illness. Bale also combined with Defoe to create a penalty that Emmanuel Adebayor converted.
The frustration for Defoe, though, is that goals do not guarantee games. Redknapp said he was a "good finisher and a good player". But when asked if the striker would keep his place for Saturday's game at Everton, the manager said: "Yes but you know Louis Saha has been scoring goals as well, he has been coming in and [he has] scored. We'll have to wait and see."
Defoe's problem is that Saha and Rafael van der Vaart are seen as more natural partners for Adebayor – the undisputed favourite. Defoe is not first choice and cannot be sure of playing in the quarter-final on Saturday week.
"It's difficult, we have a big squad," he said. "The manager knows that when called upon I'll be ready. All I can do when I get the chance is do what I do best and score goals."
This win was not as comfortable as it might sound,and not just because Spurs lost Michael Dawson to knee and ankle injuries that Redknapp assessed as "bad" after a fall and Aaron Lennon to yet another hamstring strain. Stevenage produced a performance which their manager described as "beyond the call of duty". "Every one of my players stretched themselves," said Gary Smith.
Stevenage took the lead. Rotation has costs too, as Spurs found after three minutes. Ryan Nelsen, making a third start of the season, looked utterly unprepared for Joel Byrom's dart into the area. Nelsen's tackle was late and Byrom struck the penalty past Carlo Cudicini.
Stevenage held their 4-1-4-1 shape, fought for every tackle and took their lead from their ferocious captain and centre-back, Mark Roberts. They even had a chance to score a second. Jon Ashton's leap from Lawrie Wilson's free-kick was unmatched by any of Spurs' defenders; his header sailed inches wide of the far post.
It took less than a minute for the miss to be punished. Bale fired a long diagonal pass to Defoe. The striker took the ball down with his right foot and let it bounce, deceiving Ashton, before whipping a shot in with his left.
Tottenham did produce the required improvement in the second half and three minutes in a delightful move ended with an offside Defoe backheeling the ball in at the near post.
Bale's new fondness for running inside has its critics, but one such dart sent Spurs ahead. The Welshman ran, exchanged passes with Defoe and made the byline, where he was brought down by Roberts. Michael Oliver gave the foul – Smith said it was "a shame" – and Adebayor scored.
Stevenage nearly forced an equaliser, but it was simple bad defending that cost them with 15 minutes left. The provider was Bale, with a throw-in down the line. The defence stood off as Defoe collected in the inside-left channel, shuffled inside past Ashton and curled the ball into the far corner.
Defoe sent Spurs through to the quarter-final; whether he will get to play is less clear.
Tottenham Hotspur (4-4-1-1) Cudicini; Kaboul, Dawson (Walker, 9), Nelsen, Rose; Lennon (Adebayor, 38), Parker, Kranjcar (Livermore, 81), Bale; Van der Vaart; Defoe. Substitutes not used Friedel (gk), Gallas, Modric, Dos Santos.
Stevenage (4-4-2) Day; Henry, Ashton, Roberts, Charles (Myrie-Williams, 62); Bostwick, Wilson, Byrom, Shroot; Laird, Beardsley (Reid, 62). Substitutes not used Julian (gk), Edwards, Long, May, Winn.