A former teammate of current Patriots defensive end Mark Anderson at the University of Alabama, Madison is in his sixth NFL season. He has appeared in 71 career games, most of them coming with the Pittsburgh Steelers. He was most recently with the Lions, appearing in five games this season before being released.
At 5-foot-9, 180 pounds, Madison is the type of player who would project to a third or fourth cornerback role in New England, where the team currently has second-year player Phillip Adams and four-year veteran Antwaun Molden.
That's also where Porter and McClain would potentially fit.
Porter (5-10, 205) played in six games with the Raiders this season, one of them coming against the Patriots when he had a tough time against Wes Welker. He is a second-year player out of Rutgers.
McClain (5-9, 195) is a second-year player out of UConn. He appeared in 16 games last season for the Panthers, with two starts.
Meanwhile, McBath was a second-round draft choice of the Josh McDaniels-led Broncos in 2009. He appeared in 20 career games (one start) over the 2009 and 2010 seasons.
The Patriots' safety corps has been depleted, because of a combination of injuries and personnel decisions made coming out of training camp.
The team also worked out free-agent defensive lineman Jason Parker (1st year, University of Arizona) and defensive end/linebacker Diyral Briggs (3rd year, Bowling Green).
It is common for the Patriots to work players out over the course of the season to keep emergency lists fresh.