The Vikings continued to augment their roster in free agency Sunday, adding another quarterback to back up Kirk Cousins in 2019.

According to an NFL source, the team is signing former Rams quarterback Sean Mannion to a one-year deal, bringing in the 2015 third-round pick to work behind Cousins this season. Mannion, who’s played in 10 NFL games and started one over the past four seasons, visited the Vikings in late March and joins the roster as the team’s most experienced option behind Cousins.

He’ll try to hold the No. 2 job over Kyle Sloter this season, as the Vikings remake their QB depth chart following Trevor Siemian’s departure to the Jets. Mannion comes to Minnesota familiar with the new Vikings offense, thanks to the time he spent with Rams coach Sean McVay — who mentored Cousins in Washington and was raised in the same West Coast offense principles as new Vikings assistant head coach Gary Kubiak under Mike Shanahan.

The 6-foot-5 Mannion backed up Jared Goff and appeared in three games last season, throwing just three passes. Mannion played in five games in 2017. For his career, he completed 33 of 53 passes (62.3 percent) for 258 yards, no touchdowns and one interception.

The Oregon State product reportedly scored a 40 on the Wonderlic test (a perfect score is 50, and 20 is considered average) before the 2015 draft.

Ben Goessling