After a two-week long drought, the Miami Dolphins have finally added another free agent to the roster with the signing of former Minnesota Vikings safety. Per Ben Volin , the deal is for one year.The Dolphins also re-signed exclusive-rights free agentto a one-year contract. A seventh-round linebacker out of Ohio State in 2010, Spitler has appeared in 28 games (zero starts) in two pro seasons while recording 15 tackles.The two signings give the Dolphins 60 players on the 80-man offseason roster. Restricted free agentsandremain unsigned.A Rison, Ark. native, Johnson attended Arkansas State and was a four-time All-Sun Belt selection, earning second-team honors as a freshman and first-team honors each of his final three seasons. Johnson was also a Freshman All-American and the conference's defensive player of the year as a senior.Johnson was regarded as a bit of a "tweener" coming out of college, lacking ideal size and bulk for the strong safety position but also ill-suited for a role a significant role in coverage. However, his athleticism and awareness earned him high marks from scouts and he was selected by the Vikings with a second-round pick (43rd overall) in the 2008 NFL Draft.As a rookie, Johnson started seven of 16 games and totaled 31 tackles, a fumble recovery, an interception and two pass deflections. Both his fumble recovery and his interception came in the same game, as Johnson picked offand scooped up afumble.Johnson moved into a full-time starting role in 2009, opening 15 games at strong safety oppositewhile missing one contest in December with a concussion. Although he totaled 57 tackles, an interception and seven pass deflections, Johnson graded out as Pro Football Focus' No. 44 safety with a negative grade in coverage.In 2010, Johnson appeared in just seven games with two starts, losing his job to, who was undrafted the same season Johnson was picked. He opened just three of 11 games played in 2011, recording 28 tackles and 335 defensive snaps before landing on injured reserve with a torn hamstring in late November.This isn't a signing that is going to excite the masses, but it's a solid signing that is both inexpensive and low risk. Johnson signed a one-year deal for what I would expect to be close to the minimum for a fifth-year player, but he's a former second-round pick that still has some upside at 26.Assuming he can fully recover from the torn hamstring that prematurely ended his 2011 season, I see no reason why Johnson couldn't compete for playing time at the Dolphins' strong safety job vacated by released veteranAs it stands, the Dolphins have in-house candidates like career dime backand 2009 fifth-round, who started 12 of 15 games for the Dolphins at free safety in 2011 but is regarded as potentially a better fit for strong safety.While he is by no means guaranteed a starting job or even a roster spot in Miami, Johnson is exactly the kind of low-risk/high-reward the cap-strapped Dolphins need. Expect new defensive backs coachand defensive coordinator, who was a long-time secondary coach with the Bengals, to see if they can't turn Johnson's career around.Meanwhile, the Spitler re-signing is a fairly insignificant move. He projects potentially inside or outside in the Dolphins' new 4-3 scheme, but he lacks upside and remains a pure special-teamer battling for a roster spot.Check out the updated projected depth chart reflecting these transactions here