Liriano's deal is worth $1.5 million and includes another $1.25 million in incentives, sources told baseball insider Robert Murray.
The 36-year-old spent the 2019 season pitching out of the Pittsburgh Pirates' bullpen. He posted a 3.47 ERA and a 1.36 WHIP with 63 strikeouts over 70 innings of work.
After making the All-Star Game in his 2006 rookie campaign, Liriano has jumped between the starting rotation and the relief corps in recent seasons.
That flexibility could open the door to various roles in 2020 if he reaches the majors with Philadelphia. The Phillies' rotation is set to include Aaron Nola, Zack Wheeler, and Jake Arrieta, while other candidates include Vince Velasquez, Zach Eflin, and Nick Pivetta.
Meanwhile, Walker has become something of a journeyman after spending the first seven seasons of his career with the Pirates. He played for the New York Mets, Milwaukee Brewers, and New York Yankees before joining the Miami Marlins in 2019.
Last season, the 34-year-old hit .261/.344/.395 with eight home runs and 38 RBIs in 115 games while primarily playing first base.