Jack Flaherty and the Greatest Second Half
Before or during Jack Flaherty’s start today, viewers are likely to hear about his 0.91 second half ERA. It is the third-lowest second-half ERA since 1920. The second-lowest second half ERA belongs to Greg Maddux, who accomplished the feat in the strike-shortened 1994 season and pitched barely more than 50 second-half innings. The first belongs to Jake Arrieta, whose 0.79 ERA in the second half in 2015 propelled him to the Cy Young award. Of course, ERA alone doesn’t tell the whole story. For one thing, as with Maddux, it doesn’t show how many innings are being thrown. For another, different eras produce vastly different run-scoring environments. Pitching with a juiced ball or juiced players can make life more difficult for pitchers, rendering a lower ERA even more impressive. To that end, we can put Flaherty’s second half in perspective.
The easiest way to do so here at FanGraphs is to use RA9-WAR, which takes runs allowed, innings, and the run environment into account. Flaherty’s second-half RA9-WAR was 6.4, way out in front of Jacob deGrom’s second-place 4.8 mark. If you cut Flaherty’s RA9-WAR in half, he would still rank ninth in baseball since the All-Star Break. We have second-half splits going back to 1974; here’s where Flaherty ranks among the couple-thousand qualified second-half pitchers:
| Season | Name | Team | Age | RA9-WAR |
|---|---|---|---|---|
| 1976 | Vida Blue | Athletics | 26 | 6.9 |
| 1974 | Fergie Jenkins | Rangers | 31 | 6.5 |
| 2019 | Jack Flaherty | Cardinals | 23 | 6.4 |
| 1976 | Don Sutton | Dodgers | 31 | 6.4 |
| 2004 | Johan Santana | Twins | 25 | 6.3 |
| 1998 | Roger Clemens | Blue Jays | 35 | 6.2 |
| 1998 | Randy Johnson | – – – | 34 | 6.2 |
| 1985 | John Tudor | Cardinals | 31 | 6.2 |
| 2015 | Jake Arrieta | Cubs | 29 | 6.2 |
| 1975 | Jim Palmer | Orioles | 29 | 6.2 |
| 1987 | Roger Clemens | Red Sox | 24 | 6 |
| 1975 | Gaylord Perry | Rangers | 36 | 6 |
| 1978 | Ron Guidry | Yankees | 27 | 6 |
| 2000 | Pedro Martinez | Red Sox | 28 | 5.9 |
| 1985 | Dwight Gooden | Mets | 20 | 5.8 |