Diarra has taken part in 23 Champions League, Carling Cup and FA Cup matches since joining Chelsea from Le Havre in 2005, winning 19, drawing four and losing none.
Redknapp hopes the French midfielder's amazing run continues in the FA Cup at Preston tomorrow, as his side pursue a first major trophy since being crowned league champions in 1950.
Redknapp said: "I couldn't believe it when someone told me. As soon as I did hear I knew there was no chance of dropping him. If he is that sort of lucky charm you have got to play him.
"I am not surprised, because Diarra is as good as any player I have ever worked with. He is as good as Frank Lampard, Joe Cole and Rio Ferdinand and has the potential to go on and achieve what they have."