Swearinger was released by the Houston Texans earlier this year following reports that he'd refused to play on special teams, and following repeated evidence that his on-field play did not match his status as a second-round pick. The Bucs claimed him in hopes of turning his career around, and Swearinger actually got on the field in sub packages early in the season. The safety was inactive last Sunday, though, and hasn't seen significant time on defense since week three. He did, at least, consistently play special teams.
There's no news yet on who the Bucs will sign to replace Lemon and Swearinger. Major Wright should be healthy enough to get back on the field and take Swearinger's place as the backup safety, and the Bucs don't necessarily need to add a linebacker to replace Lemon either -- they have five others on the roster. Given the team's injury-induced problems at receiver, signing one would make some sense.