West Ham are running out of patience with Marko Arnautovic after his brother accused the club of treating the player like a "commodity", Sky Sports News understands.
The club were surprised by comments made exclusively to Sky Sports News by Arnautovic's brother, Danijel, in which he claimed West Ham were "using" the player.
"He's not a cow or a horse which you bring to market," he told Sky Sports News. "He's a highly talented footballer who is simply being used by West Ham. He's just a number to them.
"West Ham were trying to get rid of Marko right up until the last minute of the January transfer window and they are still trying to sell him right now. To them he's just a commodity.
"West Ham are still speaking to the Chinese club. He is still for sale and it's simply a case of how much money West Ham can get for him."
Arnautovic signed a contract extension in January which saw his wages rise by 20 per cent to £120,000 a week.
That deal had a £40m release clause which expired on June 14, and was not activated by any club.
But Arnautovic, 30, is determined to leave east London during this summer's transfer window.
Sky Sports News was told on Tuesday that Arnautovic had handed in a transfer request, but sources at the club say they have not received a formal transfer request.
West Ham have already rejected a £19.7m bid for Arnautovic from a Chinese Super League club, Sky Sports understands - a bid the club found 'insulting'.
A sell-on clause means Arnautovic's former club, Stoke, will be due 20 per cent of any fee above £20m.
He is due to return to training with rest of squad in Switzerland on Monday.
Follow the Summer Transfer Window on Sky Sports
From July 1, Sky Sports News will be the home to three new shows dedicated to bringing you the very latest news from this summer's transfer market.
Start your day with Good Morning Transfers at 9am as our team of reporters and pundits bring you the latest news and insight. Transfer Talk then follows at midday delivering the biggest stories that matter to you. And join us at 7pm for the definitive round up of the day's news with The Transfer Show.
And as well as tuning into Sky Sports News, don't miss a thing with our dedicated Transfer Centre blog.
There's also the Transfer Talk Podcast, the daily UK, Regional and European Paper Talk, plus features across skysports.com and the Sky Sports app.