2018 Projection: Now In Philadelphia, What Can We Expect From Jake Arrieta?

by Eric Stashin (aka The Rotoprofessor)

Jake Arrieta finally found a home, ending a surprisingly long free agent period by signing with the Philadelphia Phillies.  At the end of the day he got a sizable contract, signing for three-years and $75 million, and that helps to explain why he was available for as long as he was.  It’s fair to wonder if his skills warrant this type of contract, after posting the following numbers last season:

168.1 IP
14 Wins
3.53 ERA
1.22 WHIP
163 Strikeouts (8.71 K/9)
55 Walks (2.94 BB/9)
45.1% Groundball Rate
.279 BABIP

The surface numbers are solid/strong, but as you dig in the warning bells start to ring loudly for the 32-year old:


“Lucky” Second Half
Just look at the split in his ERA last season:

  • First Half – 4.35
  • Second Half – 2.28

While you can argue that there was a little bit of bad luck in the first half (67.0% strand rate), there is no doubt that he benefited from significant luck after the All-Star Break.  With a .246 BABIP and 83.6% strand rate, does anyone believe that he can come reasonably close to the ERA he posted?


Declining Groundball Rate
He’s been a sinker heavy pitcher over the past two seasons, throwing the pitch 60.90% and 60.67% of the time.  However his groundball rate has been declining with each half:

  • First Half ’16 – 53.7%
  • Second Half ’16 – 51.1%
  • First Half ’17 – 45.7%
  • Second Half ’17 – 44.1%

That’s never a good sign, and while a move to a more pitcher friendly ballpark would’ve helped to offset it that isn’t the case.  As it is he posted a 1.23 HR/9 in ’17, including a 1.56 mark on the road.  While he may not be that bad, the risk is obviously there.


Strikeout Decline Coming?
His SwStr% took a big dip last season, with an overall 8.7% mark, and he’s seen his O-Swing% decline for three straight seasons:

  • 2015 – 34.2%
  • 2016 – 29.6%
  • 2017 – 27.9%

That’s never a good sign, and with an 8.19 K/9 in the second half it’s easy to envision a mark of 8.00-8.25 over a full season.


2018 Projection
You take all of those concerns together, you get the following projection:

180.0 IP, 13 W, 4.15 ERA, 1.27 WHIP, 164 K (8.20 K/9), 58 BB (2.90 BB/9)


Are those unusable numbers?  Of course not, but make sure you are paying for numbers closer to his 2017 first half as opposed to his second half.  There’s a lot of risk for a regression, and it’s possible the numbers get even worse than those that we have projected given the underlying metrics and risk for increased home run issues.  With a current ADP of 101.8, he’s an easy pass.

Sources – Fangraphs, Brooks Baseball

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Make sure to check out all of our 2018 Preseason Rankings:

Standard League
OBP League
First Basemen01/08/1802/09/18
Second Basemen01/15/1802/13/18
Third Basemen03/09/1803/06/18
Outfielders1-20: 03/18/18

21-40: 02/07/18
1-20: 03/12/18

Starting Pitchers1-20: 02/20/18

21-40: 02/22/18
Relief Pitchers02/12/18--

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