Chris Brunt criticised the tactics of West Brom manager Alan Pardew in a heated exchange in the dressing room after their home defeat to Huddersfield on Saturday, Sky Sports News understands.
Brunt disagreed with the decision to stick with a 4-4-2 formation, when up against Huddersfield's five-man midfield.
The Northern Ireland international also had harsh words for some of his teammates, who he accused of a lack of effort and desire.
The leak will add to the pressure on Pardew, who we understand will be in charge for Saturday's game at Watford.
But the team performance in that game could be crucial in deciding whether he remains as manager for the rest of the season.
Albion have won just once in 14 Premier League games since Pardew took over in November, and they remain seven points adrift of safety at the bottom of the table.
Brunt is Albion's second longest-serving player after James Morrison, having spent more than 10 years at The Hawthorns.