Jon Gruden said this week he expects "more drama" involving Antonio Brown ... and guess what -- he got it.
The Oakland Raiders superstar has been sued by his famous personal trainer who claims the WR stiffed him out of thousands of dollars stemming from a week-long off-season workout program.
The man behind the suit is Sean Pena -- who's been training pro athletes like Darius Leonard and MLB pitcher Matt Moore for years.
Pena somehow connected with Antonio Brown in 2019 -- and the two started working out together.