Yaya Toure's agent has criticised Manchester City's attempts to mark the midfielder's birthday with a tweet, describing their efforts as "a joke".
City gave Toure a birthday cake as they flew to Abu Dhabi and tweeted their congratulations after he turned 31.
But Dimitri Seluk says Toure is "very upset" the club's owners failed to acknowledge him personally and says he may leave over their lack of respect.
"None of them shook his hand on his birthday. It's really sick," he said.
City declined to comment officially but BBC Sport understands club officials are not too alarmed by Seluk's claims.
Seluk also claimed Toure was unhappy last summer, shortly before he signed a new four-year contract.
Seluk says Toure did not expect a present after turning 31 on 13 May but was unhappy at being ignored by the club's wealthy owners when the squad arrived in the United Arab Emirates last week to celebrate their Premier League title triumph.
"He got a cake but when it was Roberto Carlos's birthday, the president of Anzhi gave him a Bugatti," Seluk told BBC Sport.
"I don't expect City to present Yaya with a Bugatti, we only asked that they shook his hand and said 'we congratulate you'. It is the minimum they must do when it is his birthday and the squad is all together.
"I hear one newspaper has written that City congratulated him from Twitter but this is a joke. It is better they don't put anything on Twitter if they are not saying anything to him.
"The club's owners ate a 100kg cake after winning the Premier League this season but when they and the players were all together, none of them shook his hand on his birthday. It shows they don't care about him.
"Of course Yaya is upset about this. It is his birthday and nobody said anything or shook his hand, so he does not feel comfortable.
"If this happened to you as a journalist in the BBC and nobody shakes your hand, you will say bye-bye and go to work for somebody else. It is normal."
Agents do come out with a lot of shit when they're trying to weasel around for more money, but I've never seen anything quite as pathetic as these quotes