Bates had signed a new two year contract in May but a statement on the club's website on Friday morning confirmed that "due to a change in (Bates') personal circumstances he will be leaving on Sunday for Australia to join his family business out there."Glenavon boss Gary Hamilton told www.glenavonfc.com: "We're very sad to be losing Guy as he has played a major part in our advancement to where we now are and in winning the Irish Cup for the first time in 17 years."His contribution to the progress we have made has been tremendous and we will miss him, there's no doubt about that. Football is important but in the end Guy has had to make this difficult decision and I understand that completely."He has assured me that, should he ever return to Ireland, he will give us first refusal on his services."Bates hit the headlines with a flurry of goals at the beginning of last season, most notably hitting a hat-trick against derby rivals Portadown in October.Glenavon host league-leaders Ballymena United at Mourneview Park on Friday night (kick-off 7.45pm).Meanwhile, ex Coleraine and Portadown left-back Jonny Black won't rejoin the Bannsiders. He had agreed to return to Oran Kearney's side during the off-season in Australia but as his Oakleigh Cannons team are challenging for the title down under, he will not be able to return.Black's former sides meet on Friday night as Coleraine host Portadown in the Danske Bank Premiership (kick-off 8pm).