Allardyce wrote in the London Evening Standard: "The thing about Frank is that he has changed his game in recent times. He knows he can't burst forward as often as he used to so he has changed into a sitting midfielder.
"Steven Gerrard has done something similar and their experience more than compensates for the loss in energy which comes with age. They use their mind and vast know-how to walk into those spaces into which, earlier in their career, they would have run.
"Over the years, Frank's biggest contribution has been goals from midfield - not eight a season but 15 or even 20. He was almost Chelsea's second striker only playing from midfield. How do Chelsea replace those goals? It's not easy.
"Frank will still pop up in the box and score goals but he's not the man always to be released, as was the case."
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