Forecast rain may push back the former All-Star's National League debut another day. He already had it pushed back by an offseason injury to his non-throwing arm.
Liriano and the Pirates agreed on a $12.75 million, two-year contract in December. But on Dec. 25, the day before he was supposed to fly to Pittsburgh and sign the deal, he broke his arm at home in the Dominican Republic. Liriano said he was injured when he slapped a door in his house.
Pittsburgh optioned right-hander Duke Welker to Triple-A Indianapolis to make room on its 25-man roster.
Whenever he gets back, the Pirates are hoping Liriano can help fortify a rotation minus injured James McDonald and left-hander Jonathan Sanchez, who was released Wednesday.
"We're looking forward to getting him on a mound and see what the major league hitters tell us, him getting back in this environment, and see where it goes," Pittsburgh manager Clint Hurdle said.
Hurdle said the 29-year-old Liriano won't be on a strict pitch count after throwing 98 on Sunday in his third outing for Indianapolis.
After the injury, Pittsburgh revised its offer to Liriano and signed Jonathan Sanchez and Jeff Karstens to compete for jobs in the starting rotation. Sanchez was released on Wednesday, and Karstens has been on the DL all season.
Liriano has never pitched in the NL, a league that has generally been more forgiving to pitchers lately.
He was an All-Star for the Twins in 2006, when he finished third in AL Rookie of the Year voting, but hasn't been quite the same since Tommy John surgery on his pitching elbow in November 2006. Liriano won 14 games and the AL comeback player of the year award in 2010 before throwing a no-hitter for Minnesota in May 2011, but he's had control problems since then and went a combined 6-12 with a 5.34 ERA for the Minnesota Twins and Chicago White Sox last season.
"All the information we were able to gather, we felt this was a very good opportunity for him and for us," Hurdle said Friday. "We believe he's in a very good point in time in his career to have a big bounce-back."