Jameis Winston is getting backup from another NFL player who says he's positive the QB didn't sexually assault an Uber driver back in 2016 ... because he was in the car that night.
The witness is Philadelphia Eagles cornerback Ronald Darby -- Winston's longtime friend who was also a witness in JM's rape case at Florida State back in 2012.
"I felt the need to come forward and clarify some inaccurate accounts of the evening of March 13, 2016 when myself, a friend and Jameis Winston took an Uber ride in Arizona," Darby said in his statement.
"There were three of us in the car, not just one as has been reported. Myself and Jameis were in the backseat. I am confident that nothing inappropriate in nature happened in the car that evening and Jameis did not have any physical contact with the Uber driver. The accusations are just not true."
Darby went to bat for Jameis during the 2012 rape case -- straight up calling the accuser a liar during the videotaped deposition. He and Jameis have remained close ever since.
The driver told BuzzFeed she picked up Jameis from the bars in Scottsdale around 2 AM in March 13th of last year. She says he was riding alone and the QB grabbed her by the crotch during the ride.
Winston has adamantly denied the allegations and says there are holes in the driver's story -- starting with the number of passengers in the car.
The NFL says a league investigation into the incident is underway.