The 33-year old completes the move after training with the new A-League club for much of the pre-season.
“Paul’s experienced. I was happy with where he’s played in the past and the pre-season games he played.,” Ferguson said.
“He’s a leader, a good shot-stopper, he commands his box and he talks well from the back.
“I had a word with (goalkeeper) Justin (Pasfield) - he’s not far behind.
“He’s done a fantastic job in the pre-season games and he’s actually better equipped than I thought he was. He will get his opportunity."