Sunderland boss Steve Bruce claims "parasites" turned Asamoah Gyan's head with talk of joining one of European football's biggest clubs.
The 25-year-old striker was the subject of repeated speculation throughout the summer transfer window with rumours of a move to Turkey emerging as the deadline approached.
Gyan remained on Wearside and the Black Cats insist they did not receive a single offer, and now Bruce has challenged the former Rennes frontman to rediscover the form which made him an instant hit on Wearside.
The Sunderland boss is convinced the striker has not recovered from the response to his impressive display for Ghana in their 1-1 friendly draw with England at Wembley in March and the publicity that sparked.
Bruce said: "Since that game at Wembley, all the parasites, as I call them, hover around.
"People are in his ear constantly trying to engineer a deal for him.
"Certainly since the England game, when he played at Wembley so well on the night, something has been troubling him.
"It's very difficult, the constant speculation no matter what you try to quash or quell, and the people around him, the people who want to make a fast buck, shall we say, and it affects him in the end.
"He was going from Real Madrid to Bayern Munich to Valencia to Atletico Madrid.
"We have had a discussion with him and he needs now to focus and get himself back on track again and be the Asamoah Gyan we know he is capable of.
"These things affect these players, and it has affected Asa.
"I had a conversation with him two days ago to say, `Look, the window as now closed, Asa. Right, we need to see you back playing again and back the way you know you can play'."
Gyan has yet to score for Sunderland this season - indeed, the Black Cats have managed only one goal in their four games to date - and he will not end his drought this weekend after being ruled out of the Barclays Premier League clash with Chelsea at the Stadium of Light with a hamstring injury suffered on international duty.
But Bruce will have an in-from striker available after managing to push through a loan deal for Arsenal's Nicklas Bendtner, who celebrated his impending arrival in the north-east with a match-winning double for Denmark in midweek.
Bendtner, who played under the Black Cats manager as a teenager at Birmingham, could go straight into the starting line-up as he attempts to live up to his own claim that he can be one of the best strikers in world football, and that he is worth the bumper pay packet he was awarded at the Emirates Stadium.
Meanwhile, Andre Villas-Boas has shrugged off Manchester United and Manchester City's blistering starts to the season and insists his Chelsea side are good enough "to grab them".
United and City stormed to the top of the Barclays Premier League before the international break, scoring 13 and 12 goals, respectively, in their opening three games.
Chelsea are just two points adrift of their main title rivals but have managed to score only five times in their three outings, drawing 0-0 at Stoke before struggling to beat West Brom and then Norwich the Saturday before last.
The following day, they watched City romp to a 5-1 win at Tottenham and United annihilate Arsenal 8-2.
But Chelsea manager Villas-Boas was unfazed, saying: "It's good for them. They've gone on to score a lot of goals and it's good for British football.
"We just hope to score one more goal than the opponents."
He added: "Man United played to perfection and managed to score a lot.
"They are, with Man City, leading the table for the Barclays Premier League and we are two behind them.
"We want to grab them.
"Our objective is on shortening distance and not on what the others do in terms of performance."
Villas-Boas has options to freshen up his attack, with Juan Mata shining as a substitute against Norwich, Daniel Sturridge back from suspension, and Raul Meireles having signed from Liverpool on transfer deadline day.
Chelsea's defensive travails have coincided with the absence of goalkeeper Petr Cech, who looks certain to be recalled after making a swift recovery from his knee injury.
"He is lucky to be with us so quickly," said Villas-Boas, who will also be able to call upon fit-again defender David Luiz.
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