Tanard Jackson, who has been a Redskins player since 2012, has yet to play a single game with his team; that's because he is facing his fourth (yes, fourth) NFL suspension. In fact, he's been sitting out the past 20 months because of his last substance abuse related suspension and, before even hitting the 2014 season, has now tacked on another indefinite suspension.
CBS provided a handy timeline of Jackson's professional career that highlights his days on the sideline due to the almighty NFL ban-hammer. To summarize, Jackson was drafted by the Bucs in 2007 and started all but four games for the next two years due to a suspension. In 2010, he was suspended for 13 months. In 2012, he "failed a physical" with the Bucs who immediately released him. Later that year, he was picked up by the Redskins but was suspended before ever playing a game.
With another suspension tacked on, it is very likely that Jackson will never see the field again. Even if he is not suspended indefinitely, it is safe to assume that no team will risk picking the safety up.