Hull's Australian back-row forward Adam Maher will retire at the end of the season despite having 12 months still to run on his contract.
The 31-year-old former Gateshead Thunder player's resignation has been reluctantly accepted by Hull's director of rugby, Shaun McRae, who said: "I fully support and respect his decision. I know he will continue to give 100 per cent to the club for the remainder of this season's campaign, which is the only way Adam knows."
Maher makes his 100th appearance for the club when Hull take on the Tetley's Super League leaders Bradford Bulls at Odsal on Saturday evening.
The prop Chris Birchall has joined the rugby union side Glasgow from Super League strugglers Halifax on a six-month contract. He is the fifth player to leave Halifax in two months.
St Helens will be without at least 10 players for Friday's home game against Castleford and the Middlesex Sevens the following day. The forwards Darren Britt, Mickey Higham and Mark Edmondson, along with wingers Darren Albert and John Kirkpatrick, were all injured in last Saturday's win over Hull and join Paul Sculthorpe, Chris Joynt, Martin Gleeson, Paul Newlove and Darren Smith on the sidelines.Reuse content