The Detroit Lions brought in four linebackers for a workout on Tuesday, according to Dave Birkett. The full list of names hasn't been released, but we do know two of them. Birkett reported earlier that Demorrio Williams took part in the workout, and Pro Football Talk just reported that Rocky McIntosh worked out for the Lions as well.
McIntosh spent the 2012 season with the St. Louis Rams. He made nine starts and racked up 44 tackles, 1.0 sack, 1 pass defended and 1 interception. Before going to St. Louis, he was with the Washington Redskins for six seasons. Over the course of his career, he has made 78 starts.
Williams has been in the NFL since 2004. He was with the San Diego Chargers in 2012, and he started three games and finished the year with 51 tackles, 3 passes defended, 2 interceptions and 2 touchdowns. He has also played for the Kansas City Chiefs and Atlanta Falcons. Over the course of his career, Williams has started 68 games.
I'm guessing that this workout was for due diligence more than anything. Throughout the year, teams will bring in players just to get a look at what is out there in case someone goes down with an injury. If that's not the case, then perhaps the Lions aren't happy with how Ashlee Palmer, Tahir Whitehead and Travis Lewis are performing and they are searching for a veteran upgrade.
(Side note: Nick Barnett did not take part in this workout. He was apparently at Detroit Metropolitan Airport at some point on Tuesday, but he actually visited the Washington Redskins.)