Wednesday, May 13, 2009

Quality Starts

As of this morning, the Jays have the 8th best ERA (4.08) in MLB and the 4th best in the AL, a number inflated by a few starters such as Burres (no longer a Jay), Purcey (in LV trying to learn how to throw strikes) and Litsch (who ended up on the DL after just two starts). The starters have an overall ERA of 4.20, but without the three aforementioned, it is 3.18. We have been treated to a number of excellent pitching performances.

I like the Quality Start (QS) statistic, as it distils the starters’ performance down to a single number that determines whether they have kept their team in the game. 3 ER or less in 6 IP projects into an ERA of 4.50, which is close to both the mean and median numbers of runs scored per game. I make one modification to this statistic, in that I assess the QS at the end of the sixth inning, on the justification that it is a managerial decision to leave the starter in longer and if the starter gives up runs after that, he should not lose his QS. In my database I track both, and distinguish my definition from the widely-accepted definition as MQS (Modified Quality Start). In the Jays’ season to date, there has only been once that a pitcher has an MQS but not a QS: Opening night, when Halladay was allowed to continue with a big lead and gave up 4 runs in the 7th.

However, there are other measures I track as well.
• ERA in the appearance – which ignores the longevity of the start.
• Bill James’ Game Score
• WHIP+, which simply adds HBP to the on-base calculation
• BF/O, Batters faced per out which I’ve discussed before
• OPS against (OPSa)
• E(ERA), discussed below
• PQS, discussed below.

E(ERA) is Expected ERA, which is computed by determining the batting team’s Runs Created (RC) against the pitcher, which is Runs Allowed (RA). The RA are used instead of the actual ER to compute E(ERA).

PQS was developed by Ron Shandler and stands for Pure Quality Start, which assigns a 0 to 5 score based on five measures, provided the pitcher has lasted at least five innings:
• 1 if IP ≥ 6, measuring stamina.
• 1 if Hits ≤ IP
• 1 if (IP – SO) ≥ 2
• 1 if SO/BB ≥ 2
• 1 if HR ≤ 2
I have my reservations about this measure, as it is biased against pitch-to-contact pitchers that don’t strike out many, but I am going to reserve judgment until I have done more analysis.

So what have been the dominant pitching performances so far by the Jays’ starters this year?

Based on E(ERA), the top five and only sub-2.0 E(ERA) starts are
• Halladay vs NYY, May 12 – E(ERA) = 1.00
• Tallet at Oakland, May 9 – E(ERA) = 1.07
• Romero vs Oakland, April 19 – E(ERA) = 1.38
• Richmond at Minnesota, April 15 – E(ERA) = 1.84
• Cecil at Oakland, May 10 = E(ERA) = 1.85
Of course, a criticism of the E(ERA), and almost any metric, is that pitchers will get top ratings against weak-hitting teams. The OPSa metric also ranks these as the top five pitching performances.

Based on BF/O, the top five starts are:
• Halladay vs NYY, May 12 – BF/O = 1.11
• Tallet at Oakland, May 9 – BF/O = 1.14
• Romero vs Oakland, April 19 – BF/O = 1.24
• Cecil at Oakland, May 10 = BF/O = 1.25
• Romero at Minnesota, April 14 – BF/O = 1.25

There have been 10 starts with a WHIP+ of 1.00 or less. The four less than 1.00 are:
• Halladay vs NYY, May 12 – WHIP+ = 0.56
• Tallet at Oakland, May 9 – WHIP+ = 0.57
• Romero vs Oakland, April 19 – WHIP+ = 0.86
• Tallet vs Oakland, April 18 – WHIP+ = 0.94

There are 5 starts with a Games Score (GSc) of 70 or more:
• Halladay vs NYY, May 12 – GSc = 78
• Cecil at Oakland, May 10 – GSc = 74
• Tallet at Oakland, May 9 – GSc = 74
• Romero vs Oakland, April 19 – GSc = 73
• Richmond at LAA, May 6 – GSc = 70

There are 7 Pure Quality Starts with a score of 5:
• Cecil at Oakland, May 10
• Tallet at Oakland, May 9
• Romero vs Oakland, April 19
• Richmond at LAA, May 6
• Halladay at Cleveland, April 11
• Richmond vs Baltimore, May 3
• Cecil vs Cleveland, May 5

Halladay’s start last night was the best by E(ERA), BF/O, WHIP+ and GSc, yet because he only struck out 5 batters, to the chagrin of 43,737 fans hoping for a free pizza slice, his PQS is only 4. My skepticism about this measure has not waned.

This has been a great week for Blue Jays fans of great pitching!

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