Rush said: "I had the pleasure of watching Harry Kewell train alongside his new Liverpool teammates over the weekend. He is something special. He has matured a lot since I last worked with him on the training ground during my time at Leeds.
"And he has the best left foot I have seen for a very long time. He ranks alongside players like Ray Kennedy and Kevin Sheedy with his ability, but he has more pace than that duo.
"He can beat players and score goals. In short, he is a fantastic signing."