Stoke City manager Mark Hughes has claimed his West Brom counterpart Tony Pulis phoned Ryan Shawcross to call him a "loser" after their match last weekend.
The Potters' 1-0 loss at the Hawthorns was played amid a bitter atmosphere, with the managers refusing to shake each other's hands at the final whistle and Saido Berahino loudly booed by his former fans.
The level of animosity developing has now taken another turn after Hughes told a press conference that Pulis left a message for Shawcross in which he apparently insulted the Stoke captain, who he previously managed during his spell at the Britannia Stadium.
Shawcross attempted to return Pulis' call to clarify the nature of the message but could not get through, leaving Hughes to believe it was not meant as a joke.
"We were annoyed with a number of things," the 53-year-old said. "We were annoyed with their manager ringing up Ryan on the Monday morning after the game and calling him a loser.
"I wasn't too happy with that either, but hey ho. Any number of things surrounding the game were, in our view, unnecessary.
"There was a voicemail left [by Pulis for Shawcross]. I haven't heard it, but Ryan wasn't too pleased and tried to ring back and didn't get any answer."
The controversy between the two clubs began when it was revealed that Berahino, who joined Stoke in the January transfer window, had been handed an eight-week ban for failing a drug test.
Having previously been kept under wraps, the news of the sanction was leaked to the media soon after the 23-year-old had completed the transfer.
Hughes remains confident, however, that he will be able to count on the striker soon and says he is unconcerned by his previous misdemeanours.
"Under WADA (World Anti-Doping Agency) rules he wouldn't have got a ban," said Hughes. "It's the FA that include recreational and out-of-competition testing. It was a low level misdemeanour. If it was a constant problem, he would have got a longer ban.
"He's working exceptionally hard and doing work every single day. He's not unfit, just not match fit and not quite ready to start games.
"The next two weeks we can really push him on and by [the game against] Tottenham he will have more capability to cope with 90 minutes."