Mariana Kovacevic, whom they believe has at least three aliases andas many as four different addresses around Belgrade, is thought tocharge 3,000 euros for sessions treating the likes of Robin van Persieand Frank Lampard.
That is six times the average monthly take-home pay in the Serbcapital. She is not officially registered as a practisingphysiotherapist and the only Mariana Kovacevic in health authorityrecords is listed at a pharmacy in Sarajevska Street.
When Sportsmail attempted to trace her at the pharmacy, we were told:'Ah, the woman that everybody in the city is looking for? No, I don'tknow her. She doesn't work here.'
Treatment: Robin van Persie visited Kovacevic after injuring his ankle on international duty
In a case which is developing the sinister trappings of an underworldoperation, Kovacevic has disappeared without trace. The players she iscurrently treating are also being kept hidden from view by abewildering combination of subterfuge, private jets, fast cars andeagle-eyed surveillance.
Chelsea have admitted privately that Lampard flew to Belgrade on Fridayfor treatment on his damaged left thigh, yet he was not even seen atthe airport, being funneled through the VIP arrivals terminal.
The authorities believe Kovacevic regularly changes her appearance,notably her style of dressing and her hair colour in a constant effortto avoid detection.
Now that the authorities have been alerted to her existence and herdubious medical practices - notably by van Persie, who unwittinglyalerted the world at large last week - and the lack of unpaid tax, thefortysomething mother of three who is now thought to have spent timeworking for the Azerbaijan national side will be constantly sought bySerb Police.
Controversy: Lampard is one of several Premier League stars to have visited Kovacevic
Kovacevic has not been seen at her New Belgrade clinic since Wednesdaywhen Van Persie, Glen Johnson and Fabio Aurelio arrived for treatmentwhich is now understood to involve the use of electrical impulses andsmall metal sticks covered in placenta jelly penetrating the skin andthen being fed back through it.
Seven days ago, Serb sportsmen happily spoke about their visits to seeKovacevic and the miracle cures she had performed on their injuries.Now it is almost impossible to find one who will even admit to visitingher.
Partizan Belgrade's Portugal midfielder Almami Da Silva Moreira deniedseeing her, in spite of being identified by the owner of the cafe bardirectly opposite as having entered Kovacevic's clinic earlier thisseason.
Speaking after Saturday's 2-1 league win over Smederevo, Moreira said:'I haven't been to see her and I hope I don't need to see her in thefuture, but I would go. You must believe in life. If people believe inher it's a good thing. She can help them.
'Maybe the players who have seen her can't explain to their clubdoctors what she is doing there. Maybe she is doing magic things with amagic potion. If she was stopped doing what she does by theauthorities, it would be a pity for football players. It would be ashame for everybody because Belgrade is the centre of the Premiershipjust now.'
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Explore more:People:Glen Johnson, Fabio Aurelio, Frank Lampard, Robin van PersiePlaces:Azerbaijan, Portugal