Australia's Central Coast Mariners have offered sprint superstar Usain Bolt a contract, reports said Monday, but the club's coach said he knows nothing about it.

The eight-time Olympic champion has been on trial with the A-League side since August to fulfil his dream of becoming a professional footballer. He scored two goals in a pre-season friendly last week and on Thursday turned down a two-year, trial-free deal from cashed-up Maltese champions Valletta.