Gerrard netted his 100th in the draw at Newcastle United.
Rush told liverpoolfc.com: "It's an incredible achievement and all for Liverpool Football Club as well. That's another good thing. He's a bit like Carra - a one-club man.
"It's an incredible achievement from a midfielder; you expect forwards to do it, but for Stevie as a midfielder to do that is an incredible achievement.
"That goes to show how good a player he has been. For Stevie to do that from midfield shows his loyalty to the club, but also what a great goalscorer he is."
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