Jameson Taillon joins the Pirates' rotation today, and despite Neal Huntington's protests to the contrary, he seems likely to stay. That means someone needs to go, and the widely held assumption is that Juan Nicasio will move to the bullpen. That might happen, but I'm not sure it should.

Nicasio is a frustrating starter. He throws two pitches about 95 percent of the time, which makes him vulnerable against lefties and over long stretches.

Still, he hasn't been bad. Including last night's strong performance, he's whiffed a batter per inning this season while walking a very reasonable 3.6 batters per nine. His ERA is 4.50, but xFIP and SIERA mark him as something closer to 4.00 for the season. Good velocity, plenty of strikeouts, and reasonable control -- I'll take that from a starter, even if it comes with obvious downsides.

So if Nicasio stays in the rotation, who goes? The Pirates' worst starter this season has been Francisco Liriano, but he won't, and shouldn't, come out of the rotation if he's healthy -- the Bucs need Liriano to return to his previous form. Gerrit Cole is Gerrit Cole, and Jon Niese has been better lately. That leaves Jeff Locke.

Nicasio has been markedly better than Locke, Locke's decent results lately notwithstanding. Locke has a 4.28 ERA and a 47.9 percent ground ball rate, but those are about the only respects in which he's been better than Nicasio. Locke's strikeout rate, never particularly strong, has dipped to an untenable 4.7 batters per nine innings this year. That hasn't improved in his last several starts, in which he's gotten good results -- Locke has allowed just seven runs over his last three starts, spanning 22.1 innings, but he's struck out four batters total. That's not a marker of sustainable success, so Locke's recent solid-looking performances don't mean he's actually improved.

In fact, advanced stats suggest Locke has actually gotten worse this season. His xFIP is currently around five, about a run higher than Nicasio's, and his SIERA is even higher. Projection systems, too, are higher on Nicasio.