Touré may face two-year ban after positive test for banned substance

The Manchester City defender Kolo Touré faces a ban of up to two years following his suspension from playing yesterday after testing positive for a banned substance.

City, whose Abu Dhabi owners hold great store by their players' conduct, learned on Wednesday afternoon of the positive result in Touré's A sample and immediately dropped the Ivorian from the squad to face Aston Villa in the FA Cup. It is now Touré's decision whether to have his B sample, taken in the same drugs test, analysed in a bid to prove his innocence or wait for the Football Association to dispense justice.

The suggestion that the substance was found in a dietary supplement remained unconfirmed last night, with City also refusing to enter into a discussion of suggestions that the random drugs test may have been carried out after the Manchester derby on 12 February. The centre-half started against Fulham last Sunday and City would only reveal that the 29-year-old had tested for what is known under World Anti-Doping Agency regulations as a "specified substance". That is a substance "more susceptible to a credible, non-doping explanation" and raises the prospect that Touré may have been caught out by an over-the-counter medicine or dietary supplement. A dietary supplement could mean a ban lower down the scale than the nine months received by Sheffield United's Paddy Kenny, when he tested positive for the stimulant ephedrine in 2009.

The Hamilton midfielder Simon Mensing recently served a mere four-week ban after he tested positive for the stimulant methylhexaneamine, though in what is an extremely rare case the 28-year-old managed to convince the UK Anti-Doping organisation that he was the innocent victim of product contamination. Mensing's ban – only the 24th handed out in England since Adrian Mutu in 2004 and already now served – was announced only on Monday.

If a dietary supplement has been found in Touré's case, he may try to use Mensing's argument that a product had been contaminated or else that the stimulant was not on the proscribed list. The size and type of substance will define what sanctions the authorities take, if Touré is found guilty. But the drugs authorities tend to rule that sports people are responsible for any substances detected. The Scottish skier Alain Baxter, for example, was stripped of his historic Winter Olympics bronze medal at Salt Lake City and banned for three months despite proving that substances detected on him came through an inhaler.

Touré, only the second Premier League player to test positive for a banned substance – after Mutu – is the first player in any division since January 2010 to have failed a test. Most of those caught are not identified, with only the higher profile individuals tending to enter the public domain.

The news comes at a time when City are seeking to quell the image of Roberto Mancini's side as one divided, with the string of training ground bust-ups within full view of photographers not helping the situation.

Touré has looked more solid this season than last. And with Vincent Kompany's return for Saturday's game at home to Wigan uncertain, the club can ill-afford Touré's absence, but as one of the players inherited from Mark Hughes he has never seemed a long-term prospect. His City career may now be over, with the chances of playing again this season seeming to be in doubt.

Players who have failed drugs tests

Diego Maradona Argentina's captain was suspended for 15 months in 1991 following narcotic use while at Napoli. He was given a similar suspension during the 1994 World Cup after testing positive for ephedrine.

Edgar Davids Dutchman tested positive for anabolic steroid nandrolone while at Juventus in 2001. Served a reduced four-game ban.

Jaap Stam Dutch defender tested positive for nandrolone after departing Manchester United for Lazio in 2001. Banned for five months and fined £30,000.

Adrian Mutu The striker was given a £20,000 fine and a seven-month ban in 2004 following his admission he took a banned substance. He was sacked by Chelsea as a result.

Paddy Kenny The QPR goalkeeper tested positive for ephedrine and was suspended for nine months while at Sheffield United in September 2009.

Simon Mensing Hamilton Academicals midfielder was suspended for four weeks this year after testing positive for stimulant methylheaneamine, found in dietary supplements.