Redknapp wrote in The Sun: "Spending huge amounts of money on a striker doesnâ€™t guarantee you goals.
"Fernando Torres has proved that in recent seasons. But this year he has quietly been sneaking up the charts. He now has 19 goals this season â€” he is in the top five.
"The days of Clive Allen scoring 49 goals in one campaign are gone in England. Defences are much better organised and strikers really have to put in a shift off the ball as much as on it.
"If you analysed Cliveâ€™s game, and Iâ€™m sure he wonâ€™t be offended, he was no good in the air, had no pace and couldnâ€™t dribble one on one. Yet he was a superb finisher.
"These days thatâ€™s not enough. Jimmy Greaves was a world-class marksman and could get 35-40 goals a year.
"But in the modern game it is even harder to score against defenders who are quicker and more comfortable on the ball.
"So, 19 goals from Torres is a good return. If you have a striker on your books who gets you 20 goals per season then you have to be satisfied."