Doug Martin -- a former running back who last played in the NFL in 2018 -- has died ... TMZ has learned.
A source with direct knowledge confirmed to TMZ Martin passed away recently ... though they did not share any further details.
Martin was a standout RB at Boise State for four years before the Tampa Bay Buccaneers drafted him in the first round of the 2012 NFL Draft.
He played six seasons in Tampa Bay during which time he was twice named to the Pro Bowl and once received All-Pro honors.