Vincent Jackson likely died on or before Feb. 13 -- two days before he was discovered by law enforcement -- this according to a new death report, obtained by TMZ Sports.
The former NFL star was pronounced dead on Feb. 15 after hotel staff contacted police about an unresponsive male in a room at the Homewood Suites in Brandon, FL.
Cops had been investigating and now say hotel staff saw Jackson in the same room -- in the same slouched position -- as early as Feb. 13 ... but assumed he was sleeping.
But, on Feb. 15, a housekeeper began to realize the sad reality -- Jackson wasn't resting, he was dead -- and someone at the hotel dialed 911.
When cops arrived at the scene, they confirmed Jackson had died.
As for visible injuries, cops say he had a small laceration on his left big toe -- but that's it.
The death report also notes Jackson had a history of alcohol use, but was not a known drug user.
As we previously reported, Hillsborough County Sheriff Chad Chronister announced earlier this week that Jackson likely died from issues connected to "chronic alcoholism."
Jackson had been living at the Homewood Suites hotel since January ... and his family had become concerned about him -- even filing a missing person report on Feb. 11.
Cops made contact with him at the hotel on Feb. 12, but determined he was okay. Sadly, he was not okay, and seemingly died hours later.
He was only 38.