Steelers Pro Bowl receiver Antonio Brown lashed out at the coaching staff on the sidelines in Sunday's defeat and failed to show up for meetings on Monday, extending a turbulent period with the team that dates back months, according to team and league sources.

Brown became irked with head coach Mike Tomlin back in training camp when he was no longer able to have an individual trainer and personal social media manager on the field, sources said, and the trainer was eventually booted from campus at Saint Vincent College after clashing with the team's strength staff. In the early days of camp, Brown had seemingly constant access to those individuals – men who team officials knew little about and who had no formal ties to the organization – including directly during practice sessions.

Brown was displeased when informed they could no longer have the sort of access they had become accustomed to. Shortly thereafter he returned to Pittsburgh for an "evaluation" for an "undisclosed injury," but some in the organization – at the time and to this day – believe Brown's absence for a few days may have had more to do with his emotions over his associates being kicked off the field than any minor quad injury that kept him from practice for a few days.

"Maybe it's a coincidence, but the timing of that seems a lot like what just happened on Monday," one source said.

Brown was also among a very small group of Steelers who spoke out in at least relative support of star running back Le'Veon Bell's decision to stay away for the regular season and not sign his franchise tag – at a time when several offensive linemen ripped the running back publicly – and there has been tension between him and the team brewing throughout the summer. Furthermore, offensive coordinator Randy Fichtner is calling plays for the first time – he has a very close relationship with quarterback Ben Roethlisberger and the Steelers have been the most pass-heavy team in the NFL – and the lack of balance and consistency in the offense has not gone unnoticed by Brown and others.

Ultimately, the coaches and front office believe Brown wants nothing more than to win, I'm told, and are confident that much of this tension will dissipate if/when the team gets back to its winning ways. Should it fester, however, there certainly could be more fireworks to come from Brown and others in what has been a fairly turbulent locker room in recent years.