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| Is Noah Syndergaard a future #1? |
Defining rotation slots based on ERA-, FIP-, and xFIP-.
When
talking about baseball, it’s common for the discussion to turn to starters and
rotations. Even though the distinction is often being made arbitrarily, people
like to refer to pitchers as ‘a number 2 starter’ or ‘an Ace’ or even ‘a great
5th starter’ to help define roles within a rotation, and help
compare strengths of rotations. It doesn’t have to be completely arbitrary
though, as we can use metrics to define rotation slots. But which metrics are
best to use? I am not the biggest fan of pitcher WAR, and this has been done
before with pitching
bWAR anyway – although they took a different approach than I will here. Also,
I wanted to use inning independent statistics, and since ERA-, FIP-, and
xFIP- are league and park adjusted, I think they were the best choices.
Considering
there are 5 starters per team and 30 teams, I wanted to consider about 150
pitchers for this group – such that the top-30 would be #1 starters and so on.
This meant that I had to lower the inning minimum to 80 IP as a starter for the
season, which is about half of a season’s worth of starts, just to get the
group to include 150 starters. When I lowered the inning minimum to 70 IP, the
group increased from 153 to 161, and the ERA- max in 2014 decreased from 173 to
135 (with FIP- and xFIP- following a similar pattern), which seemed more
realistic. Almost all teams will need more than 5 starters during the season, and
only about 88 have qualified for the ERA title per year in the 2000’s, but it
was a little surprising that I had to lower the limit to 80 innings as a
starter to reach 150 starters. Also, lowering the inning limit to 80 IP as a
starter led to an average of 147.5 starters/season over the last 20 seasons, or
149 over the last 13 seasons. This speaks to how valuable it is just to have a
healthy pitcher who can consistently keeps the team close for 5-6 innings/game
throughout the season. I added an extra group to the normal 1-5 starter slots
in Table 1, listed under ‘Rank – 1-5,’ which is for the ‘True Aces’ of the
majors.
Table 1 – 2014 slots, minimum 70 IP as a starter.
Rank
|
ERA-
|
FIP-
|
xFIP-
|
1-5 (Ace)
|
48-61
|
51-66
|
56-68
|
6-30 (#1)
|
63-80
|
70-86
|
69-86
|
31-60 (#2)
|
80-92
|
86-94
|
87-96
|
61-90 (#3)
|
93-100
|
95-104
|
97-105
|
91-120 (#4)
|
100-114
|
104-113
|
105-110
|
121-150 (#5)
|
114-135
|
113-125
|
110-121
|
As
you can see, of the 150 best starters who threw at least 70 innings in 2014, more
than 60% in the group were: within 20% of the league average ERA, within 14% of
the league average FIP, and within 13% of the league average xFIP. All of the pitchers
within the group of 4th starters are already below league average by
these standards, and 3rd starters push the limits of being average. The
5th starters group stretches from the limits of what’s acceptable to
the limits of a team’s patience – the ERA story paints a much worse picture,
and it’s harder for a team to overlook, than the xFIP story. More data is
needed to get a clear picture, which is why I look back at the last 20 seasons
in Table 2 (13 seasons for xFIP-). If you’re interested, an image of the
distribution curve for ERA-, FIP-, and xFIP- is shown in Figure 1.
First,
let’s take a quick peek at where Mets starters ranked within these groups last
year. The Mets had 5 starters who threw at least 137.1 IP in 2014, so they all
easily qualify for the dataset. Jacob deGrom easily led the way in all three
groups, and he qualified for the #1 starters group in each statistic (78
ERA-/76 FIP-/82 xFIP-). Jon Niese falls into the 3rd starter group
by ERA- and xFIP- (both 98), but drops to the 4th starter group by
FIP- (105). Zack Wheeler just missed the 3rd starter cut by ERA-
(102), was a 3rd starter by FIP- (101), and reached the 2nd
starter group by xFIP- (95). Dillon Gee had the lowest FIP- (129) and xFIP-
(114) among Mets starters, and fell into the 5th starters slot for
ERA- (115) and xFIP-, but missed the cut by FIP-. Finally, Bartolo Colon was a
5th starter by ERA- (118), but a 3rd starter by FIP-
(102) and xFIP- (100). In summary, the Mets had the following: 1, 3, 4, 5, 5 by
ERA-; 1, 3, 3, 4, 5 by FIP-; 1, 2, 3, 3, 5 by xFIP-.
 |
| Figure 1 – Shape of the distribution curve for ERA-, FIP-, and xFIP-. |
For this graph, ERA-, FIP-, and
xFIP- are on the y-axis, and the major gridlines on the x-axis separate the
starter slots. Aces fall to the left of the dark line, and guys who should be on
the verge of being cut fall to the right of the red line. Notice that within those lines the slope is pretty steady.
Table 2 – ERA- and FIP- slots based on data from 1995-2014
(3,000 pitchers), xFIP- slots based on data from 2002-2014 (1,950 pitchers),
minimum 70 IP as a starter.
Rank
|
ERA-
|
FIP-
|
xFIP-
|
Top 3.3% (Ace)
|
(25)-63
|
(28)-69
|
(52)-74
|
3.3-20% (#1)
|
63-82
|
69-87
|
74-89
|
21-40% (#2)
|
82-93
|
87-96
|
89-97
|
41-60% (#3)
|
94-104
|
96-104
|
97-103
|
61-80% (#4)
|
105-117
|
105-113
|
104-110
|
81-100% (#5)
|
118-144
|
113-132
|
111-123
|
I
put the lowest total in parenthesis because that was just the lowest from this
group, and an Ace could potentially be even better. Notice that xFIP has a
smaller spread than FIP- and much smaller than ERA-, which is what we saw in Table
1. The picture becomes a little clearer when you have more data, and we can
make a few rough guidelines from Table 2:
1)
Aces are 60 ERA-, 70 FIP-, and 75 xFIP- or
better,
2)
#1 starters are 80 ERA-, 85 FIP-, and 90 xFIP-
or better
3)
#2 starters are 90 ERA-, 95 FIP-, and 95 xFIP-
or better
4)
#3 starters are 105 ERA-, 105 FIP-, and 103
xFIP- or better
5)
#4 starters are 115 ERA-, 115 FIP-, and 110
xFIP- or better
6)
#5 starters are 140 ERA-, 130 FIP-, and 120
xFIP- or better.
Of these rules, the upper limit put on 5th starters ERA- is
probably the hardest to accept, as it sounds too high, and is a big jump over
the #4 limit. But, for a Mets starter in 2014, a 140 ERA- was equal to just
under a 5.00 ERA, and that’s not so high that a team who believed in the
starter (or was paying him a lot) wouldn’t let him keep pitching.
Of
course, there is more to being a starter than just having a good ERA (or FIP or
xFIP) when you pitch, you also have to be able to pitch for your team every 5
games, and deep enough into starts to not keep draining the bullpen, for an
entire 162-game schedule. This list is nearly half starters who wouldn’t
qualify for their seasons ERA title – either because they were injured, in the
minors, or just stunk and were let go. Still, nearly 75% of the starters in
Table 2 went at least 130 IP, which is about 2/3 of the season, and a valuable
total for their teams. While these rotation slots are not based on an ideal
sample of 150 pitchers with 162+ IP, they are based on actual results, so the guidelines
are still useful as at least a rough estimate. At the very least, this should
make you rethink the value of a guy who can throw 200 innings, even if he’s
pitching at a rate 20% worse than league average.
Astronomy Cast Podcast Ep. 369: The Fizeau Experiment http://t.co/Dx6S3xWOpK pic.twitter.com/ksqV0BJnUq
— Universe Today (@universetoday) March 20, 2015
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