(photo credit: Brian Curski, Cumulus Media)

This is a series of evaluations that will be done this offseason on every player that closed the season on the 40-man roster for the Minnesota Twins throughout the winter until each player has been evaluated. The plan is to start with Mr. Belisle and move all the way through the pitchers, then to the catchers, infielders, outfielders and finally those listed as designated hitters on the club’s official MLB.com roster. That means we’ll wrap it up with Kennys Vargas sometime before the season starts.

  • Name: Tyler Duffey
  • 2017 Role: One of the team’s better relievers despite ERA, though his penchant for blowups — even if infrequent — made him hard to trust late in games. He still worked plenty of high-leverage spots.
  • Expected 2018 Role: He’ll have a lower profile in the bullpen to start, but the talent is still there for him to pitch key innings late in games.
  • MLB Stats: 4.94 ERA, 3.72 FIP in 71 innings; 8.5 K/9, 2.3 BB/9, 1.37 WHIP, 0.7 fWAR, minus-0.4 bWAR.
  • MiLB Stats: N/A
  • Contract Status: Arbitration-eligible for the first time after 2018, free agent after 2011.

2017 Lowdown:

The move to the bullpen for Duffey was met roundly with praise, as the expectation was that the 26-year-old righty would see his homer problems vanish, his velocity tick up and his ERA come down while smoothing out some of the kinks that saw him post a ghastly 6.43 ERA in 2016 — a season almost all the Twins would rather forget.

The move to the bullpen was a good one for Duffey, even if it wasn’t abundantly clear. His ERA dropped nearly two full runs, and all of the indicators in his secondary stats improved as his mostly two-pitch repertoire, as it turns out, was better suited for work in relief. The fastball velocity didn’t really take off for Duffey, but he averaged 92.1 mph on his four-seamer — up from 90.4 the year before — and his two-seamer was up nearly two full ticks from the 90.3 mph he averaged 2016. He cut off a bit of the usage on his curve and changeup, but for the most part, he stuck to the script of what he did as a starter, and by and large, it went OK.

Outside of the ERA that is better suited bringing passengers north and south on the west side of the metro, everything else in his profile looks encouraging. He continued inducing grounders above the league-average rate (49.5 percent), struck out just under a batter per inning, kept his walks down and managed to reverse his home-run trend (1.69 per nine to 1.14) at a time when the league was going in the other direction. That all adds up to a 3.72 FIP, but a 4.94 ERA.

So, why?

It wasn’t really that Duffey had any obvious rough patches, as his splits don’t really look like a guy who had one really bad month to sully the rest of his season.


ERA by month

  • April – 1.59
  • May – 5.02
  • June – 4.05
  • July – 7.36
  • August – 4.66
  • September – 7.15

ERA by location

  • Home – 5.14
  • Away – 4.75

ERA by half

  • First – 4.81
  • Second – 5.14

Nothing seems totally out of whack here. While he did have a few odd months of OPS against — 1.022 in July, .927 in September but then .630 or lower in each of the other four months — it wasn’t like there was a barrage of homers against him at a bad time, either. He didn’t allow a long ball in April, then allowed at least one — but never more than two — every month the rest of the way.

So what’s the deal?

For the year Duffey allowed opposing batters to hit .275/.317/.404. That’s…..fairly reasonable. Righties hit .294/.325/.383 and lefties .243/.305/.439. Neither really jump off the page, which is good because sometimes two-pitch righties can struggle with left-handed hitters. The slugging percentage jump for lefties makes sense because of him allowing a groundball rate of 56.1 percent to righties and just 38.3 percent to lefties. In short, he’s exchanging contact (.294 average) for power (.383 slugging, .089 isolated slugging) against same-sided hitters, which his pitch splits indicates that he probably throws more curves (62.5 percent groundball rate) and two-seamers (47.7 percent) than four-seamers (32.4 percent) to righties. Does it mean anything?

Probably, but most likely, he has his reasons.

But there’s an interesting thing in his splits, and it’s one I’m not sure how to fix. Duffey’s strand rate in 2017 was just 66.7 percent, which is in line with his career rate of 66 percent but well below the AL average of 72.6 percent. For relievers, that bumps up to 73.3 percent.

Where that factors in for his FIP is that it assumes a possibility of his strand rate normalizing, which would bring down his ERA in this case. What that also can mean, however, is that a pitcher struggles to pitch with runners on base.

Here are Duffey’s splits from last year, via Fangraphs:

  • Bases empty – 8.8 K/9, 1.2 BB/9, 1.00 WHIP, 3.00 FIP, .219/.248/.316 line against (.245 wOBA)
  • Men on base – 8.2 K/9, 3.0 BB/9, 1.97 WHIP, 5.54 FIP, .357/.400/.571 line against (.407 wOBA)
  • Men in scoring position – 9.6 K/9, 5.8 BB/9, 2.80 WHIP, 5.73 FIP, .429/.494/.657 line against (.462 wOBA)

The comps for each of those situations, as best as I can explain in order, are Alcides Escobar’s 2013 season (.247 wOBA), the first year Mike Trout should have won the MVP (2012 with a .409 wOBA) and Bryce Harper’s unbelievable 2015 MVP season (.461 wOBA). Not great!

The short answer is that Duffey wasn’t good at pitching with runners on base in 2017. From his career numbers, we can see this is….kind of a thing:

(both photos courtesy of Fangraphs.com)

What’s troubling is that a lot of times this can be attributed to struggling with pitching out of the stretch. Well, here’s Duffey working in relief last year with the bases empty — and he’s not in the windup.   

Here’s Duffey working as a starter in 2016, and he’s coming out of the wind-up with the bases empty:

Basically, what I’m saying here is that it doesn’t seem to be something mechanical. But the Twins have hired Josh Kalk away from the Tampa Bay Rays in addition to pitching gurus across all levels, so their goal this offseason — among others, of course — will be to see if they can find the special sauce to get Duffey to pitch better with runners on base.

It won’t be easy — but the payoff could be huge.

Grade: C+. Duffey pitched a lot of good innings for the Twins in 2017, but not enough to soak up the bad ones that made his season look so-so on the surface.

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