Liriano, who slots in at No. 20 on MLB.com's Brewers top prospects list, became available when the Padres designated him for assignment on Friday to make room for free-agent acquisition Alexei Ramirez.
"We believe [Liriano] is someone who adds to our outfield depth," said Brewers GM David Stearns. "He is out of options, so he will come to Spring Training and compete for a spot on the team. He has the ability to play all three outfield positions, so that versatility will help him."
Liriano has made most of his professional starts in right field, but also has extensive experience in center, which is one of Milwaukee's most uncertain positions at the Major League level. At Triple-A El Paso last season, Liriano batted .292 with a .383 on-base percentage, 14 home runs and 18 stolen bases.
Seidenberger, 23, was a 12th-round Draft pick in 2013. He posted a 3.06 ERA and five saves in 22 games at advanced Class A Brevard County before a promotion to Double-A Biloxi.
To make room for Liriano on a full 40-man roster, the Brewers designated outfielder Shane Peterson for assignment. Peterson briefly served as Milwaukee's starting center fielder last August under former general manager Doug Melvin.
"Shane is a guy who we believe has value," said Stearns. "We're at the point now where every time we add someone to the 40-man roster, we have to make a tough decision as to who comes off. Shane is a Major League player. He has proven that. I'm confident he will get opportunities again, whether it's with us or elsewhere."
Adam McCalvy is a reporter for MLB.com. Follow him on Twitter @AdamMcCalvy, like him on Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.