Hay is a half decent striker who has often been injured. He has played for Celtic, Swindown, Huddersfueld (where he was used as a winger) and the other Saints in the past and has scored a decent number of goals. If he stays fit then he might not be too bad, but the chances of him staying fit are unlikely.
Meanwhile, Saints have reportedly made an enquiry about Dundee United's James Grady, who will be joining the United squad for the pre-season tour in England.
Story source: The Paisley Daily Express