Contemplating Tyler Duffey

Tyler Duffey is back in the majors, having taken the berth previously occupied by Andrew Vasquez. He threw two scoreless innings on Tuesday after the Twins fell behind; it wasn't exactly a mop-up assignment, but it wasn't high leverage either.

The intriguing aspect to Duffey's return is his declared de-emphasis of his sinker (two-seam fastball). His focus is going to be pairing curves with four-seam fastballs up.

Duffey made a splash in the final two months of the 2015 season as a starter. He used two different curves -- one sharp and faster, one bigger and slower -- and two different fastballs -- two- and four-seamers -- and went 5-1 with a 3.10 ERA down the stretch.

What we don't see in that mix is a straight changeup. Neil Allen, then the Twins pitching coach, was really big on changeups. Duffey spent spring training the next year working on a changeup. He spent 2016 in the rotation -- 26 starts, second most on the team -- but put up a 6.43 ERA in 133 innings.

So 2017 found him in the bullpen, where he spent most of his collegiate career before the Twins drafted and signed him out of Rice. He was good for about a month and a half working multiple innings with two or three days off between outings, but things got rough when the thinness of the bullpen prompted manager Paul Molitor to start using him on consecutive days. And he's had just 27 major league innings the past two seasons combined.

My sense on Duffey's repertoire is complicated:

• Two different curves and two different fastballs should be sufficent variation.
• There hasn't been a notable velocity difference between Duffey's two- and four-seam fastballs.
• There also doesn't seem to be much movement on his two-seamer.
• If a pitcher has two pitches of similar velocity and movement, he doesn't have two useable pitches. Duffey may grip them differently, but the hitters don't care.

This is a oversimplification, but as a general rule, pitchers who throw four-seamers are going for strikeouts; pitchers who throw two-seamers are looking for weak contact. Duffey's four-seamer isn't all that fast, but if he can command it in the upper part of the strike zone, it's doing something different than his curves, which are supposed to bend and drop.

Command is the key. Keep that four-seamer up, change the hitter's eye level, and use that curveball. He needs a good run here before some of the injured relievers start coming back -- especially since Ryne Harper gives the Twins another right-hander who specializes in curves.