Through August 21, Velasquez' next-best start rates a game score of 72 – meaning his April 19 performance is 35% better than any other game he's pitched in the majors. Not only is his 16-K performance an outlier to this point in his career, it's one of the biggest outliers in baseball history (min. 25 career starts).
For those who don't know, Game Score is a scale developed by Bill James to rate the quality of a pitcher's start. In a nutshell: Every start begins with a baseline of 50. Points are added for positive events like strikeouts and completed innings; points are deducted for negative events like runs, hits and walks allowed. A GSc between 50-60 roughly equates to a "quality" major league start. A GSc of zero (or below) is historically bad; a GSc of 100 (or above) is historically good (there have only been 13 nine-inning games that rated a GSc of 100 or more). It's not really a stat with any practical application, but it's a fun way to try and answer a question like "Who had the better 20-strikeout game – Kerry Wood or Randy Johnson?" (It was Wood). If you're interested in more details on how GSc works, check out this article by Jeff Angus.
The two highest game scores of all time were generated by opposing pitchers in the same game: Joe Oeschger of the Boston Braves faced off against Leon Cadore of the Brooklyn Robins on May 4, 1920, and the 4000 fans in attendance on this overcast afternoon got their money's worth: Oeschger and Cadore each went the distance in a 26-inning affair. This monumental struggle was left unresolved when the game was mercifully and sensibly called on account of darkness (a modest Oeschger reminisced decades later, "Maybe too much credit has been given to Cadore and me for going so long. The hitters were having a difficult time trying to pick up the pitches in the late innings because it was almost dark.")
The duration of this 26-inning affair? Three hours and fifty minutes. Oeschger and Cadore pitched the equivalent of three major league games in less than four hours (the average ML game time this year is just about three hours). Pitch counts? HAH. They LAUGH at your "pitch counts." Oeschger faced 90 batters over those 26 innings; Cadore battled 96. Between them, they threw upwards of 700 pitches.
For his efforts, Oeschger generated a GSc of 153; Cadore trailed at 140. Obviously, this was the game of a lifetime for both men: Oeschger's second-best game took place in three seasons earlier, a 14-inning shutout good for a GSc of 102 (exactly 50% worse than his career best); Cadore's next-best GSc was produced less than two weeks prior to his monumental 26-inning effort: a nice 87, meaning that Cadore's best career game was 61% better than his next-best game. It's the largest delta in baseball history.
Of course, Oeschger and Cadore created their shared masterpiece in the waning days of the Dead Ball era, playing a game that bears little resemblance to the one we know today. In fact, eight of the nine highest game scores in history were recorded prior to 1921, as were almost all of the largest Game Score Deltas (GScD). So in order to gain a truer measure of the great outliers – and Vince Velasquez' unique achievement – let's look at "flukiest" games pitched in the post-integration era (1947 – present).
- Al Aber - Best Game: 101; Second-Best Game: 69. GScD: 47%
A left-handed mop-up man who made the occasional start for Detroit, Aber's 15.1 IP, 1-run effort against the White Sox on August 13, 1954, was the uncontested pinnacle of his six-year career (Aber took the loss when Minnie Minoso tripled home the winning run in the bottom of the 16th inning). His second-best game came in his very next start: A nine-inning, two-run complete game victory over the Cleveland Indians. On a relative basis, Aber's best game was 47% better than his second-best – the largest delta since 1947.
- Rob Gardner - Best Game: 112; Second Best Game: 80. GScD: 40%
Rob Gardner's effort on Oct. 2, 1965 (15IP/5H/0R/7K/2BB), is the very definition of an outlier, and stands as perhaps the unlikeliest great game ever pitched. A journeyman reliever/spot-starter (the lefthander toiled for six teams over the course of his eight-year career), Gardner started but four games for the Mets in 1965, failing to make it past the sixth inning in any but this all-time gem.
- Vern Law - Best Game: 118; Second Best Game: 87. GScD: 36%
"Kill the Win" indeed – and call it the "Vern Law" rule. Pittsburgh's Law pitched the game of his life July 19, 1955: 18IP/9H/1ER/2BB/12K. After 18 innings of grit and guile, an exhausted Law was lifted from the game. Bob Friend was brought in to start 19th. Friend promptly gave up a run—and the lead—on two hits and a walk. The Pirates scored two in the bottom of the 19th to take the game, giving Friend "the win." A friend indeed. Law's second-best game occurred almost 10 years later, with 12 shutout innings against Philadelphia. Once again, "The "Deacon" didn't factor in the decision, watching his bullpen cough up the game in the 14th.
- Vince Velasquez – Best Game: 97; Second Best Game: 72. GScD: 35%
As measured by Game Score Delta, Vince Velasquez' April 19th gem stands as the fourth "flukiest game" since 1947. What makes Velasquez' achievement unique is the relative degree of difficulty: It's much harder to generate game scores that approach or exceed 100 in today's game (GSc is tied directly to IP – the last starter to go even 10 innings in a game was Cliff Lee in April of 2012), so scores are usually clustered within a much tighter range.
The talented young pitcher can take some solace in the fact that he won't stay on this list very long. Velasquez will no longer be among the game's great outliers with his next strong start (say, 7IP/3H/0R/8K/1BB). But for now, he can claim ownership of one of the more unique games in baseball history.