Jonathan Mayo

What to expect from Pirates' Glasnow in big leagues

Club's No. 1 prospect called up to make start Thursday

What to expect from Pirates' Glasnow in big leagues

A Tyler Glasnow callup in 2016 has been firmly in the "when, not if" column. It appears that the "when" is Thursday, in St. Louis, when the big right-hander will take his spot in Pittsburgh's rotation, at least for this time around.

Glasnow, the Pirates' No. 1 prospect (and No. 8 overall), will start on Thursday against the Cardinals, with the rest of the Bucs rotation being pushed back one day. There's a chance this will be a one-start deal, with both Gerrit Cole and Jameson Taillon expected to return after the All-Star break. Even so, there is plenty of excitement about what the No. 2 right-handed pitching prospect in the game might bring to the table.

There is absolutely no question about the 6-foot-8 starter's ability to get Major League hitters out, with as electric stuff as any pitching prospect in the game. It starts with a fastball that sits in the mid-to-upper 90s, which is a premium velocity he maintains throughout his starts. Glasnow misses a ton of bats with his fastball, both in and out of the strike zone, and he uses his huge frame extremely well to throw downhill and with sink.

Complete Pirates prospect coverage on

Glasnow's secondary offerings have come a long way since he was drafted as a tall and skinny ultra-projectable right-hander in the fifth round of the 2011 Draft (the Pirates gave him an above-slot $600,000 to sign). His power curveball is a nasty pitch when he throws it for strikes, another potential out pitch. Last year, when he returned from an ankle injury, Glasnow struggled with his breaking-ball command. The silver lining there was he was forced to throw his changeup more as a result, and that offspeed pitch is now Major League average.

Top Prospects: Glasnow, PIT

The 22-year-old is one of the most unhittable starters in the Minor Leagues, with a career .172 batting average against. Glasnow has held Triple-A hitters to a .176 BAA this season and continues to strike them out a very high rate (10.6 per nine innings in 2016, 11.5 in his career).

The only negative in Glasnow's ledger, and it's something he has worked tirelessly to improve over the course of his career, is his walk rate. Command and control have long been an issue, and after vastly improving his walk rate in 2014 and '15 (3.5 per nine a year ago), it's jumped up a bit this year (4.9). Clearly, he's still been effective, as he leads the International League in strikeouts (113 in 96 innings) and is third in ERA (1.78). But while Glasnow has gone at least six innings in each of his past four starts prior to his callup -- two of them being hitless outings -- his issues finding the strike zone have kept him from pitching deep into games at times.

Whether it's just for one start or whether Glasnow sticks around, that's all it comes down to for him. If he throws enough strikes, he is ready to dominate hitters at any level. At some point, Glasnow will fit in nicely behind Cole atop the Pirates' rotation.

Jonathan Mayo is a reporter for Follow him on Twitter @JonathanMayo and Facebook, and listen to him on the weekly Pipeline Podcast. This story was not subject to the approval of Major League Baseball or its clubs.