Patterson, 30, played for the Orioles in 2006 and '07, batting a combined .273 with 24 homers and 98 RBIs in 267 games in that span. He signed a Minor League deal with the Mariners in December, but opted out on March 31 upon being told he wouldn't make the team to start the season.
Last year, Patterson played in 113 combined games for the Triple-A affiliates of the Brewers and Nationals, batting .292 with 12 homers, 62 RBIs and 21 stolen bases. In 16 total games in the Majors for those clubs, he went 3-for-29.
Orioles left fielder Felix Pie is expected miss three months with a ruptured latissimus dorsi muscle -- the largest muscle in the back -- which created a need for another outfielder at Triple-A Norfolk, with Lou Montanez now in the Major Leagues.
For his 10-year career, the lefty-hitting Patterson has a .252 average with a .290 on-base percentage.
Alden Gonzalez is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.