Gem: A Pitching Masterpiece

June 12, 2011

Last week, we evaluated the definition of a Quality Start and concluded that, while still useful, it is seriously flawed. This week, we’re going to introduce an alternative: Gem.

In the baseball vernacular, broadcasters and writers use the term "Gem" regularly to describe a pitching masterpiece: "Felix Hernandez pitched a gem last night in the Mariners’ 2-1 victory over the Tigers." Bill James took that term and gave it a definition. The end result is an improvement on Quality Start and a way to highlight the best pitching performances.

A Gem is a game in which the starting pitcher earns a Game Score of at least 65 or throws six or more innings of shutout baseball. For the mathematically inclined, we’ll go over the definition of Game Score at the end of the Stat of the Week, but first let’s show some examples of what a 65 looks like. Shaun Marcum earned a Game Score of exactly 65 in his start last Tuesday against the Mets. He went 6.0 innings, struck out one and allowed two hits, no earned runs, and four walks. Kyle Kendrick’s start against the Braves on May 7 also earned a Game Score of exactly 65. He threw 5.0 innings, struck out three and allowed two hits, no earned runs and one walk. Both of those games qualify as gems, albeit at the lowest end of the Game Score spectrum.

On the higher end of the spectrum is Justin Verlander’s no-hitter earlier this year. On May 7 against the Blue Jays, he went the distance with no hits, no runs, a walk and four strikeouts. His performance earned a game score of 90, but that was not the top pitching performance of 2011. Here are the top Gems of the season:

Top Five Gems of the 2011 Season
Date Opponent IP H ER BB
Game Score
James Shields
5/22 Marlins 9.0 3 0 1 13 93
Clayton Kershaw
5/29 Marlins 9.0 2 0 1 10 92
Cliff Lee
4/14 Nationals 9.0 3 0 1 12 92
Dan Haren 4/12 Indians 9.0 1 0 2
8 91
Ian Kennedy
4/25 Phillies 9.0 3 0 0 10 91

In a Major League season there are 2,420 games. Over the last ten years there have been an average of over 2,300 Quality Starts per year. That’s almost one per game. There are about 1,000 Gems per year. Just under 50 percent of MLB games are a Gem.

Gems and Quality Starts – Last 10 Years
Through June 12, 2011
Quality Starts 22,438
Team Winning Percentage in a Quality Start .679
Team Winning Percentage in a Gem

Teams win two-thirds of the time when the pitcher has a Quality Start, but while there are fewer Gems, the winning percentage is much higher at .815. As we saw last week, when a pitcher throws a Quality Start of eight innings or fewer with exactly three earned runs, the team winning percentage is only .500. While there aren’t that many Gems with three earned runs, the winning percentage in the 164 games over the last ten years is .689.

The 2011 leaders in Quality Starts and Gems are:

Quality Start Leaders   Gem Leaders
Pitcher, Team Quality Starts   Pitcher, Team Gems
Justin Verlander, Tigers 13   Justin Verlander, Tigers 9
Jered Weaver, Angels 12   Shaun Marcum, Brewers 8
Roy Halladay, Phillies 12   Roy Halladay, Phillies 8
Cole Hamels, Phillies 11   Randy Wolf, Brewers 7
Dan Haren, Angels 11   Jered Weaver, Angels 7
Jair Jurrjens, Braves 11   Felix Hernandez, Mariners 7
James Shields, Rays 11   Cole Hamels, Phillies 7

For more on Gems, visit

Below is the formula for Game Score, the foundation for Gems, and here is the link for the Wikipedia article on Game Score.

Start with 50.
Add 1 point for each out recorded by the starting pitcher.
Add 2 points for each inning the pitcher completes after the fourth inning.
Add 1 point for each strikeout.
Subtract 2 points for each hit allowed.
Subtract 4 points for each earned run allowed.
Subtract 2 points for an unearned run.
Subtract 1 point for each walk.

The 12-point penalty for allowing three earned runs reduces the chance that a pitcher can reach a game score of 65, the benchmark for a gem. As I said last week, only allowing three earned runs keeps the team in the game, but it is far from the quality suggested by the term Quality Stat. Gems are a much better way of recognizing superb pitching performances.


COMMENTS (1 Comment)

if an event occurs 1,000 times out of 2,420 games, it seems that calling it a "gem" is a bit of hyperbole. a gem implies rarity, and 1,000/2,2420 is not rare. anything occurring more frequently than, say, 10% of the time seems to preclude it from being referred to as rare.
5:17 PM Aug 17th
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