What’s the next step for Cardinals pitcher Jack Flaherty?

Jack Flaherty had a case as the best pitcher in baseball down the stretch last year, but what’s the next step for the Cardinals’ young ace?

Jack Flaherty had a solid first full season with the St. Louis Cardinals in 2018, as he posted a 3.34 ERA, a 10.8 K/9 and a 3.5 BB/9 over 151 innings. He finished fifth in NL Rookie of the Year voting, with better things all but sure to come in 2019.

However, Flaherty’s anointed breakout campaign started with a dismal thud. During the first half of the season, he went 4-6 with a 4.64 ERA and a 1.23 WHIP over 18 starts (97 innings). But the All-Star break seemed to come at the right time.

In the second half of 2019, Flaherty had a 0.91 ERA and a 0.71 WHIP over 15 starts (99.1 innings). His K/9 rate jumped from 9.9 to 11.2 from the first half to the second half, while his BB/9 rate went from 3.0 to 2.1. Most notably, he allowed 20 home runs in the first half and just five in the second half, as his strikeout/walk ratio improved dramatically (3.34 in the first half; 5.39 in the second half).

Flaherty’s second-half surge requires deeper examination. His 27.6 K-BB ratio was fifth-best in baseball during the second half, with a BABIP (.206) and a strand rate (94.2 percent) that were the best marks in baseball over that span. Regression toward the general mean, a strand rate in the 70-75 percent range and a BABIP allowed closer to .290 or .300, is surely coming over a full season.

That said, Flaherty is good at limiting hard contact. His average exit velocity (86.1 MPH), hard-hit rate (30.3 percent) and wOBA (.254) were in the 91st, 91st and 93rd percentiles last year according to Baseball Savant. If he ceded more ground balls (39.5 percent last year) and fewer fly balls (38.3 percent in 2019, according to FanGraphs), it’s possible he’d allow even less good contact. There may be some possibilities there.

Flaherty’s curveball was not a good pitch for him last year (-1.2 runs above average, according to FanGraphs), and he threw it 12 percent of the time. Statcast data shows the spin rate on the pitch was only middle of the road (51st percentile), and a discerning eye on the zone maps might say he operated too high with it.

Flaherty threw his sinker basically as much as his curveball last year (11.9 percent; literally four fewer pitches per Baseball Savant). While it was an effective pitch for him (9.8 runs above average, per FanGraphs), the Statcast zone map shows Flaherty also left his sinker up more regularly than seems ideal.

Operating lower in the zone hardly guarantees inducing discernibly more ground balls. But for someone of Flaherty’s ilk, as he allows so little hard contact anyway, the gap between his ERA (2.75) and FIP (3.46) from last year might have narrowed with the more refined location of his curve and sinker.

The curve and sinker accounted for a solid chunk of Flaherty’s pitch deployment in 2019 (23.9 percent combined). So the improvement in the margins of those pitches–particularly his curveball, the pitch on which he allowed the highest slugging percentage on last year (.354)–should allow Flaherty to take another step in 2020. Just don’t expect a repeat of last year’s second half.