Mark Bosnich has been given a week by English premier league club Chelsea to explain how he tested positive to cocaine or face the sack.

The Australian goalkeeper was given the ultimatum yesterday after the Football Association confirmed his B sample came back positive.

Bosnich is expected to plead his innocence and claim he has no idea how the drug entered his system.

He has been suspended without his STG42,000 ($A119,000) a week pay since his A sample tested positive last month.

Bosnich has played seven games in two years at Chelsea, and has not played in over 12 months, after plummeting to third choice keeper at Stamford Bridge.

He has one year left on his lucrative contract but the club has been seeking a way to offload the expensive spectator for some time and this will provide the perfect opportunity.

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