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Guardiola's quit threat

Guardiola insists he never knowlingly took nandrolone

The Spain international initially failed a routine test after the league match with Piacenza on 21 October and was subesquently suspended.

A further test revealed another positive result following the match against Lazio on 4 November.

"I have to demonstrate that I have not taken any substance," the former Barcelona player said.

"If I cannot manage to do that in the next four months, then I won't carry on playing."

The 30-year-old, who was recently recalled to Spain's national team, said he had not lost his appetite for the game.

But he added could not carry on playing if people questioned his integrity.

"There is no player that wants to play more than me, but before I return I have to prove my innocence," Guardiola said.

"I can't play thinking that there are people out there who believe I am taking some form of banned substance.

"I am totally innocent and do not want any deals to reduce a possible ban.

"All I want to do is show that I have never knowingly taken a banned substance."