The 35-year-old left-hander agreed to a minor league contract with the team on Monday that includes an invitation to big league camp. If added to the 40-man roster, he would get a one-year contract paying $1.8 million while in the major leagues and $150,000 while in the minors.
He also could earn $1.5 million in performance bonuses based on a points system based on appearances, the length of appearances, starts and games finished.
Pittsburgh traded Liriano to Toronto on Aug. 1, 2016. He went from Toronto to Houston at the 2017 trade deadline and earned a World Series ring while working out of the bullpen for the Astros. Liriano spent 2018 with the Detroit Tigers, going 5-12 with a 4.58 ERA in 27 games.
The Pirates appear set at the top of their rotation with Jameson Taillon, Chris Archer, Trevor Williams and Joe Musgrove. Liriano could pitch his way into the mix for the fifth spot if he can regain the form he showed during his first tour with Pittsburgh.