Medjani, who was seen as a future prospect upon his arrival in the summer, won a place in Gerard Houllier's senior squad for the FA Cup tie at Portsmouth after a series of impressive performances for McAuley's second-string side.
McAuley said: "Carl is looking more assured game by game. He is using the ball well, is good in possession and doing very well.
"He is learning fast and making a real contribution."