Liriano (3-0) struck out nine and walked just one to remain unbeaten since making his season debut against the New York Mets two weeks ago. Mark Melancon survived a bumpy ninth inning for his first save of the season.
Andrew McCutchen doubled twice for the Pirates and scored the game's only run on an RBI single by Garrett Jones in the first. Pittsburgh has won 10 of 12 to move 10 games over .500 (28-18).
Chicago's Jeff Samardzija (2-6) nearly matched Liriano pitch for pitch, giving up just three hits in seven innings, but received no help. The Cubs have dropped four of five.
