Vincent Jackson's Death Hit Close to Home

Ryan Leaf didn't know Vincent Jackson personally but almost died the same way -- alone in a hotel room -- and he's begging Roger Goodell to do more to help former players cope.

The former NFL quarterback posted an emotional video Monday in the hours after Jackson passed away at the Homewood Suites hotel in Brandon, FL. Officials say Jackson had suffered from chronic alcoholism.

Now that he's had time to process the situation, Leaf spoke with TMZ Sports about why Jackson's death had such a tremendous impact on him, despite the fact they didn't know each other,.

"I just was really emotional. I can relate," Leaf says ... "There was some empathy behind it because he was alone in a hotel room dying…