The Dolphins announced Thursday that they signed free-agent S Tyrell Johnson.
Johnson, who visited Miami earlier in the week, spent the first four seasons of his career with the Vikings. Last season, he played in 11 games with three starts, recording 28 tackles and one pass defensed.
His most productive season came in 2009, when he started 15 games and made 57 tackles and seven passes defensed. Johnson helps fill a void at safety created when the Dolphins cut veteran SS Yeremiah Bell.
The team also announced that ILB Austin Spitler signed his exclusive-rights free-agent contract.