Leathersich owns a 3.65 ERA in 12 1/3 innings over 18 big league appearances. He made one appearance for the Cubs on July 6, allowing two runs on four walks and a hit while recording two outs.
Leathersich will report to Indianapolis as the team prepares for the International League playoffs. He is under club control for at least five more years, but there is a chance he could join the Pirates later this month.
He was originally selected by the Mets in the fifth round of the 2011 Draft. He made his Major League debut for New York in 2015, going 0-1 with a 2.31 ERA, 14 strikeouts and seven walks in 17 appearances, but then had Tommy John surgery in July 2015.
Leathersich owns a career 3.30 ERA in the Minors and averaged 14.9 strikeouts, five walks and 6.6 hits allowed per nine innings. As a high-strikeout pitcher with command issues, he fits the Pirates' typical "upside" target. Pitching coach Ray Searage has had success working with pitchers who possess high-end stuff but struggle to control it.
It's unclear how Leathersich fits into the Pirates' long-term plan as they begin looking toward 2018. They have a young bullpen core set to return next season with closer Felipe Rivero, Dovydas Neverauskas and Edgar Santana. Right-handers Daniel Hudson, George Kontos and A.J. Schugel are also set to return.
That leaves a lack of lefties in front of Rivero, a hole that could be filled by a converted starter like Steven Brault, Leathersich or another acquisition.
Around the horn
• Rivero was unavailable Monday against the Cubs after throwing 31 pitches in the ninth inning of the Pirates' 3-1 win over the Reds on Sunday.
• Kontos, on the disabled list with a right groin strain, is scheduled to face hitters Tuesday. If all goes well, the Pirates could activate him as soon as Wednesday or Thursday. He will be used as a setup man alongside Neverauskas and Hudson.
• The Pirates' Double-A Altoona affiliate clinched the Eastern League's Western Division title on Monday.
• This is the first time since 1997 that the Pirates have had five 100-strikeout pitchers on their staff. Now: Gerrit Cole, Chad Kuhl, Ivan Nova, Jameson Taillon and Trevor Williams. Then: Jon Lieber, Jason Schmidt, Esteban Loaiza, Francisco Cordova and Steve Cooke.