Friedrich, 28, has a career 5.81 ERA in 100 games spread over three seasons with the Rockies (2012, '14-15).
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In February, Friedrich was designated for assignment by the Rockies. He was then claimed by the Angels, only to be returned to Colorado when the waiver claim was reversed due to questions over his medical evaluation with the team.
"It doesn't happen a lot," Angels manager Billy Eppler said. "Where you do see it happen is in the offseasons, when there's a time lapse between a player's last game and the next time that player is in front of people again."
Padres manager Andy Green said Friedrich is still getting his arm in shape and is up to throwing at 90 feet. Green thought Friedrich has been slowed by a shoulder issue.
"He's a long-term play for us," said Green, who noted Friedrich could be ready to pitch in Cactus League games later this month.
"He's going to be a guy we're going to invest in throughout the year and make sure he's healthy before he gets introduced to a rotation spot or introduced to bullpen competition."
Friedrich was the second lefty the Padres added on Thursday, as the club also inked veteran reliever Matt Thornton to a Minor League deal with an invite to big league camp.
The 25th overall pick in 2008 out of Eastern Kentucky University, Friedrich reached the big leagues in May 2012. He made his first start against the Padres at Petco Park, allowing one earned run over six innings with seven strikeouts.
Friedrich went 5-8 with a 6.17 ERA in 16 starts that season before missing the last two months and most of 2013 with a stress fracture in his lower back.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.