When the All-Star break arrived in early July, Jack Flaherty did not head to Cleveland for the Midsummer Classic festivities.

He wasn’t snubbed, overlooked or left out. The Cardinals right-hander, coming off a fifth-place finish in the 2018 National League Rookie of the Year voting, had endured a frustrating first half that featured a 4.64 ERA and eight starts with at least four runs allowed.

Flaherty’s last outing before the break was frustrating in its own way, as he took a hard-luck, 1-0 loss at San Francisco. But the performance was a turning point, with Flaherty taking a no-hitter into the seventh inning and ultimately allowing just one run on two hits.

Following that start, and coming out of the break, Flaherty has been the most effective pitcher in the Majors. In fact, he may be in the process of putting together one of the best second halves for a starting pitcher in MLB history.

This red-hot stretch earned Flaherty NL Pitcher of the Month honors for August, and it could be pushing him into at least the periphery of the NL Cy Young Award conversation. It also has led a second-half revival for the Cardinals, who entered the break at .500 but have gone 38-20 since to claim a four-game lead in the NL Central.

Here is a closer look at Flaherty’s amazing run, which he will look to continue on Saturday against the Brewers.

In rare territory

In 11 second-half starts, Flaherty has thrown 71 1/3 innings and ranks first in the Majors (minimum 50 innings) with a 0.76 ERA and a .150 opponent average, second with a 2.18 FIP and 3.0 FanGraphs pitching WAR, fourth with a 0.76 WHIP and sixth in the gap between his strikeout and walk rates (26.9%).

The season is not over. Flaherty likely will get three more regular-season starts, or perhaps four if the Cardinals are playing meaningful games until No. 162. He might hit another rough patch. But at this point, Flaherty’s second-half run prevention ranks as some of the best any regular starting pitcher has produced since the All-Star Game first divided the season in 1933.

Lowest ERA in a 2nd half
Min. 70 IP, since 1933

1. Jake Arrieta (2015 CHC): 0.75 ERA in 107.1 IP

2) Jack Flaherty (2019 STL): 0.76 ERA in 71.1 IP
3) Kris Medlen (2012 ATL): 0.94 ERA in 95.1 IP
4) Roger Clemens (1990 BOS): 0.97 ERA in 92.2 IP
5) Tom Seaver (1971 NYM): 1.10 ERA in 139.1 IP
6) Spud Chandler (1943 NYY): 1.12 ERA in 121 IP
7) Bob Gibson (1968 STL): 1.19 ERA in 144 IP
8) Johan Santana (2004 MIN): 1.21 ERA in 104.1 IP

Flaherty has thrown far fewer innings than those other pitchers, which is a factor to keep in mind.

At the same time, he also is dealing with a difficult league environment, with the NL as a whole having a 4.42 ERA in the second half. Four years ago, when Arrieta clinched a Cy Young Award with his breathtaking run, the NL’s second-half ERA was 4.07. And it was a mere 2.99 in 1968, when Gibson finished off the lowest single-season ERA of the live ball era and helped force the lowering of the mound. In the above group, only Santana played in a league with a higher baseline.

As the overall ERA suggests, Flaherty has been lights-out basically every time he has taken the ball since that early-July game in San Francisco. The 23-year-old has not allowed more than two earned runs in any of those outings and has produced seven scoreless appearances out of his last 10.

Combine that with Flaherty’s persistent stinginess with hits, and you get an active 12-game streak in which he has not allowed more than two earned runs or six hits. That’s something only three other pitchers have done within one season since the live ball era began in 1920 -- although the feat clearly has become more achievable due to recent trends across the game.

12 straight GS, no more than 2 ER + 6 H
Since 1920 (within one season^)
Jack Flaherty (2019 STL): 12 GS, 0.80 ERA
Chris Sale (2018 BOS): 13 GS, 0.87 ERA
Jake Arrieta (2015 CHC): 13 GS, 0.57 ERA
Felix Hernandez (2014 SEA): 12 GS, 1.31 ERA
^Excludes openers

“Every time he takes the mound, I feel like he’s going to throw a no-hitter,” veteran teammate Adam Wainwright said before Flaherty blanked the Pirates over eight innings in his last start.

Road to success

No pitcher goes on a roll of this magnitude without benefiting from some good fortune. Certainly that’s true of Flaherty, who has allowed a mere .206 average on balls in play and stranded nearly 96% of his baserunners over these past 12 starts -- with help from a stellar Cardinals defense.

Even so, Flaherty isn’t exactly getting by with smoke and mirrors. Of the 99 starting pitchers who have faced at least 200 batters since July 7, only the dynamic Astros duo of Justin Verlander and Gerrit Cole have been better than Flaherty in terms of expected wOBA (.236), a Statcast metric that factors in strikeouts, walks and quality of contact (based on exit velocity and launch angle).

After his most recent out, Flaherty credited his streak to some small mental adjustments and better execution. Here’s a couple of ways those may be taking shape:

• While Flaherty’s overall pitch usage has not changed much, he does seem to be attacking left-handed batters a bit differently. From the first half to the second half, he has replaced some four-seam fastballs with sinkers targeting the lower outside corner, and ramped up his slider usage at the expense of some curveballs and changeups.

The adjustment seems to be working. Since July 7, lefties are 3-for-49 (.061) with no extra-base hits and 18 strikeouts against the sinker-slider combo. Overall, lefties have gone from hitting .272/.335/.519 in Flaherty’s first 17 starts, to a paltry .139/.192/.197 over his past 12.

• Prior to that July 7 turning point, opponents were squaring Flaherty up with some regularity, despite the quality of his stuff. The 36.7% hard-hit rate against him was only about league average, and opponents were barreling a healthy 9% of their batted balls, one of the highest rates for a regular MLB starter. Flaherty was yielding a .459 slugging percentage and more than a home run per start.

Since then, Flaherty has been much better at avoiding the fat part of the bat. He ranks among the MLB leaders in hard-hit rate (25.3%) and barrel rate (4.0%), while cutting his opponents’ slugging percentage in half and allowing just four homers.

That ability to limit quality contact has helped drive the sort of dominant stretch that few pitchers are ever able to put together. And as St. Louis looks to clinch its division and snap a three-season playoff drought, it couldn’t have come at a better time.