Lefthander Blake Snell allowed just four earned runs in his final three starts and 15 innings at Triple-A Durham, yet that stretch of 2.40 ERA pitching—which, mind you, was more than a full run lower than the International League average of 3.62—cost him a chance to make history.
Through his first 22 appearances and 119 innings, Snell had allowed a mere 17 earned runs, which meant that he entered play on his Aug. 25 start with a 1.29 ERA that matched Justin Verlander for the lowest such mark by a minor league pitcher in nearly a quarter of a century. Verlander accomplished that feat in 2005, when he zoomed through high Class A Lakeland and Double-A Erie en route to his big league debut with the Tigers on July 4.
Snell, a 22-year-old Rays prospect, did not fall far on the minor league ERA leaderboard. He settled into second place with an ERA (1.410) that tied lefthander Jon Connolly, in his 2003 season at low Class A West Michigan, to three decimal places. Snell’s brush with history helped him earn recognition as the Minor League Player of the Year.
Here are the top 10 composite ERAs posted by minor league pitchers since 1993, the first year in which the BA Almanac takes note of overall minor league leaders. That distinction is important for players who play for multiple minor league clubs in one season, as Snell did in 2015, which he began at high Class A Charlotte before advancing to Double-A Montgomery and, finally, to Durham.
Note that Josh Beckett in 2001 was the only pitcher on this list, other than Snell, to win the Minor League POY award. Also note that every pitcher on the list at least reached the majors, save for the still-prospect-eligible Snell and Glenn Sparkman. (Yes, even Dilson Torres drew a big league paycheck, having logged 44 innings for the 1995 Royals.)
Incidentally, this top 10 ranking of ERAs also constitutes all the qualified pitchers to record an ERA of 1.60 or lower during the past 23 seasons.
Now, to approach the numbers form a different angle. These are the ERA leaders in the same order as above, with each pitcher’s highest level from that season, plus his innings count at each classification of the minors and his rate of batters faced per game.
|2||Connolly||1.41||2003||West Michigan (MWL)||166||—||—||—||166||26.3|
|4||Cunnane||1.43||1994||Kane County (MWL)||139||—||—||—||139||16.9|
Here we see that Snell is the only pitcher to face a Triple-A batter in his record-challenging ERA season. In fact, the vast majority of innings among this group came from pitchers at the lowest levels of the full-season minors: high Class A (42 percent) and low Class A (33 percent). Therefore, the degree of difficulty for Snell’s ERA achievement must be the highest in the sample.
While the Rays managed Snell’s workload carefully, especially when he reached Triple-A in late July, he still faced an average of nearly 21 batters per game, a rate that places him squarely in the middle of the pack for these ERA challengers. And only Connolly, who spent all year in low Class A, faced a significantly higher workload than Snell.
Add it all up, and Snell, who also led the minors with a .182 opponent average and ranked among the overall leaders with 15 wins (third), 163 strikeouts (fourth) and a 1.02 WHIP (ninth), had one of the best minor league pitcher seasons of recent vintage.