Sabermetric Primer: QS%

February 23, 2010 3:02pm CST

After spending PART I of this short two-part series looking at the Quality Start (QS) detailing its ins and outs, I will spend PART II describing to you that while knowing QS numbers are valuable on their own, it's the context in which these outings were produced that really speaks to the value of the measure, and be inference the value of the hurlers.


QUALITY START PERCENTAGE

A Quality Start, defined as six or more innings pitched with three or fewer runs allowed, is a measure used to record a pitcher's ability to keep his team in the game. However, like many other measures, it is limited in that it is just a number with no context attached. Without this context it's virtually impossible to discern the true value of the measure, so in order to do that with the Quality Start, let me give a quick example of how we can add the needed context to the QS to make it a useful measure.

In 2009, Chris Carpenter and Roy Halladay both had 22 Quality Starts, so if you only had that information it would be impossible to come to any other conclusion than they were equal in terms of performance in '09. Of course, we know this isn't true because there is much more to being a good pitcher than just producing a QS with things like wins, ERA, WHIP, K/BB etc. needing to be considered. However, in a vacuum where only QS is considered, you would have to agree with the previous statement that they were equal last season. That's why it is so important to place this and all measures in context because with context we no longer see just the edges of the painting, we are able to see the entire landscape of the canvas.

When it comes to the QS, the context that we need to consider is the overall times that a hurler took the hill as a starting pitcher. In so doing we are able to find the needed framework to determine what the QS number actually means. Here is the vital information we need to add to the QS total of 22 to find some truly useful data with which to draw a conclusion in our comparison.

Carpenter made 28 starts in 2009.
Halladay made 32 starts in 2009.

Consequently, doesn't it stand to reason that Halladay should have had more QS since he was able to take the hill four more times? We can measure this situation by placing those QS in the context of Games Started (GS) and therefore deriveQuality Start Percentage (QS%), to help us answer the question of who was the more "quality" starter in 2009.

To determine QS% we take the pitchers' QS total and divide it by his total games started (GS).

QS / GS = QS%

Therefore, we can determine Carpenter and Halladay's QS% by the following simple equations:

Carpenter: 22 QS / 28 GS = 0.79

Halladay : 22 QS / 33 GS = 0.69

What this means is that 79% of Carpenter's starts were considered a QS whereas Halladay's percentage was just 69%. As a result we can say that even though both pitcher's raw total of 22 QS were the same that Carpenter was more effective in producing QS in that he did so in 10 percent more of his starts than did the new Phillies' ace.

Hopefully this brief explanation has got your mind working. Here is our revised QS table which lists the hurlers by their QS% and not merely the raw total of QS that each guy posted last season.


2009 QUALITY START %
(Minimum 162 IP)

Pitcher	GS	QS	QS%
Felix Hernandez	34	29	0.85
Tim Lincecum	32	26	0.81
Zack Greinke	33	26	0.79
Chris Carpenter	28	22	0.79
Ted Lilly	27	21	0.78
Jair Jurrjens	34	25	0.74
Adam Wainwright	34	25	0.74
Dan Haren	33	24	0.73
Ubaldo Jimenez	33	24	0.73
Jon Lester	32	23	0.72
Cliff Lee	34	24	0.71
Randy Wolf	34	24	0.71
Wandy Rodriguez	33	23	0.70
Josh Johnson	33	23	0.70
Bronson Arroyo	33	23	0.70
Jon Garland	33	23	0.70

Felix Hernandez leads both the raw total, and percentage lists. Both numbers, 29 and 85 percent, are rather startling since only five times last season did he fail to produce a QS (in each of those five outings he allowed at least five earned runs).

The NL's best pitcher, Tim Lincecum, was the only other hurler in baseball with a mark above 80 percent.

Chris Carpenter and Zack Greinke tied in third spot, a fitting spot for each considering both led their league in ERA (Greinke at 2.16, Carpenter at 2.24).

Ted Lilly vaults way up the list because, like Carpenter, he was limited in his start total despite being extremely effective at posting QS.

The rest of the list has many of the "names" that one would expect to see on the list as no one else had fewer than 23 QS last season.

A few other hurlers worthy of being mentioned follow.

69 percent- Chad Billingsley and Javier Vazquez
Two workhorse type hurlers who both posted 22 QS in 32 starts.

68 percent - Johan Santana
He might have been limited to 25 starts because of injury, but he still posted a solid number that equaled the mark of Phillies' hurler Joe Blanton.

67 percent- Kevin Correia
The Padres' hurler had a nice season as he used his home ballpark to great advantage (3.68 ERA, 1.25 WHIP). Overall his QS was better than the marks posted by guys like Joel Pineiro (66 percent) and Edwin Jackson (64 percent).

63 percent - Justin Verlander
The lowest finisher who had at least 22 quality starts last year.

61 percent - Matt Cain, J.A. Happ, Ryan Dempster, Carlos Zambrano, Jarrod Washburn, Jered Weaver
Cain was great. Happ was solid but could regress in 2010. Dempster and Zambrano were teammates in Chicago. Washburn - he is still looking for a team. And finally we have the case of Weaver. A fly ball pitcher who is often victimized by the long ball, he was the lowest qualify in terms of QS% amongst hurlers who had at least 20 QS last year.

50 percent - Jason Hammel
He was the lone qualifier, at least 11 quality starts, who finished with exactly a 50/50 mark.

47 percent- Cole Hamels
Will have to pitch a lot better in 2010. Many of his underlying factors were much off his 2009 levels, but he did experience a substantial drop off in this category (70 percent with 23 in 33 starts last year).

35 percent - Rick Porcello
Throws a lot of grounders, but his output could be suspect if the team once again limits his innings pitched per outing (only once in his last 12 outings did he last seven innings, and seven times in that stretch he didn't even reach six innings).

31 percent - Jonathan Sanchez
Boom or bust. He was either lights out or had no idea what he was doing - at least in the first half. Later in the year, he really seemed to have figured some things out with a 3.83 ERA and a 1.24 WHIP over his last 15 starts.


So is Quality Starts or Quality Start % a life-changing bit of information that will become an indispensable tool in your fantasy toolbox? Certainly not. Still, it can be another one of the tools in your toolbox as you move toward building your team for the 2010 season and that has to be worth something, doesn't it?