When Jack Flaherty struck out an AL-record seven straight batters to begin the game against the Cardinals on April 30 and struck out a career-high 14 hitters against his former team, we got a glimpse at the old version of Flaherty.

Flaherty burst onto the scene with the Cardinals in 2018-19 -- a stretch where the right-hander from Southern California had a 3.01 ERA in 61 starts, finished fifth in NL Rookie of the Year voting in the first year and fourth in Cy Young Award voting in the latter year. The fact that he did so in his age 22-23 seasons made it all the more impressive for what looked like a burgeoning ace.

Flaherty’s career went a bit off the rails after his ’19 season, however, largely due to injuries that limited him to just 154 2/3 innings from 2020-22. But even his return as a full-time pitcher in 2023 yielded results that were a far cry from his peak years, a season where Flaherty had a 4.99 ERA in 29 games for the Cardinals and Orioles.

Flaherty signed a one-year deal with the Tigers over the offseason and has so far rewarded Detroit with a 3.88 ERA and 63 strikeouts in 48 2/3 innings heading into his start on Saturday night at Arizona. What’s even more encouraging is Flaherty has underlying ERA indicators that show his run prevention could be even better going forward.

Flaherty’s 2.11 expected FIP -- which looks at a pitcher's FIP but uses projected home-run rate instead of actual home runs allowed -- is tops among qualified starters. Flaherty’s 2.98 expected ERA -- based on an opposing hitter’s quality and quantity of contact -- also pegs him as a top-20 starter, as does his 2.94 FIP. Essentially, his 3.88 ERA is good, but it could be much better.

Here’s how Flaherty has seemingly put his career back on the right track and gotten back to his old ways.

More whiffs and chases

A big part of Flaherty’s early success was his elite ability to miss bats and finish off hitters with punchouts. Across 61 starts during those two years, Flaherty struck out 413 batters, a figure that only trailed nine other starters. Among pitchers to throw 300 innings in that time, Flaherty’s 29.8 percent strikeout rate was better than all but six starters.

That number dropped considerably following the 2019 season and -- given how long he wasn’t pitching like that guy -- it was maybe fair to assume that version would not be coming back. This year, however, the right-hander is back to his bat-missing ways.

Flaherty from 2018-19: 29.8 K%, 31.0 whiff%, 28.9 chase%
Flaherty from 2020-23: 24.1 K%, 27.9 whiff%, 24.5 chase%
Flaherty in 2024: 32.5 K%, 35.5 whiff%, 31.3 chase%

Even this is a notch above what Flaherty did in his best seasons. Flaherty’s 35.5 percent whiff rate is tops among the 130 pitchers who’ve thrown 30 innings this year, while his 32.5 percent strikeout rate is only behind Garrett Crochet, Tyler Glasnow and Dylan Cease.

Flaherty’s chase rate isn’t quite as impressive but his 6.0 percent increase from last year is the biggest jump among that same group of pitchers. His 31.3 percent chase rate would also represent a career high by a comfortable margin (he’s never finished above 30 percent for a season).

Return of the dominant slider

If you’re looking for one reason Flaherty is generating so many whiffs again, look no further than his slider regaining form. When he was at his best in 2018-19, Flaherty’s slider was one of baseball’s best pitches.

Only 10 individual pitches generated more whiffs (399) than Flaherty’s slider during that time, while only eight pitches produced a higher whiff rate (45.4 percent). In terms of expected wOBA -- based on a hitter’s quality and quantity of contact -- only 15 pitches (min. 400 PA) produced a lower mark than Flaherty’s slider (.241).

Flaherty’s slider started to lose effectiveness following the 2019 season. It was merely good from 2020-22 and turned into one of baseball’s worst pitches last season.

Among the 138 breaking balls or offspeed pitches that were thrown 500 times last season, Flaherty’s slider allowed the second-worst batting average (.339) and slugging percentage (.558). After never dipping below a 35 percent whiff rate in a single season before last year, Flaherty’s slider produced whiffs on just 26.5 percent of swings in 2023.

Flaherty has reversed that trend in a big way this season. Opposing hitters have a measly .669 OPS against Flaherty’s slider this year and are once again swinging through plenty of them (40.2 percent whiff rate). Flaherty has leaned more into the pitch, too, throwing it a career-high 31.3 percent of the time.

While the pitch characteristics haven’t changed much, the location of the slider certainly has. Take a look at how Flaherty’s slider location has changed, broken down by his 2018-19 seasons, his down season in 2023 and his current season.

Paired with a great knuckle curveball that never left -- Flaherty’s offering has a career 41.3 percent whiff rate and was at 40.2 percent last year -- the right-hander has two excellent secondaries to miss bats. Flaherty has produced the fifth-most strikeouts (36) on breaking balls this season, which is only behind Cease, Chris Sale, Sonny Gray and Glasnow.

Many of those whiffs are coming on breaking balls out of the zone, which hitters are chasing more than ever this season. Flaherty is getting hitters to chase nearly 40 percent of the time against his slider and curveball. When hitters are chasing Flaherty's breaking balls out of the zone, they’re missing on 61.5 percent of swings and have a .401 OPS.

Interestingly enough, Flaherty’s four-seam fastball is the least effective it’s been in his career, despite having the best velocity (93.8 mph) since 2020. Flaherty is producing plenty of whiffs (28.5 percent) and the four-seamer is his top strikeout pitch (27), but hitters have an .798 OPS against the pitch (.718 career mark).

Flaherty has also mixed in his changeup more than ever, throwing it a career high 4.9 percent of the time.

Pounding the zone

Flaherty’s success hasn’t just been about getting his slider and strikeouts back. He’s also commanding the ball like he never has before.

Flaherty was never known for throwing a ton of strikes, even when he was at his best. He entered the season with a career 9.1 percent walk rate, with that figure spiking to 10.8 percent from 2022-23. This year, Flaherty is among the league’s best at limiting free passes.

Flaherty is walking hitters at a 3.1 percent clip, which is bested by only two qualified pitchers: Zach Eflin (1.8 percent) and George Kirby (2.5 percent). That figure is more than twice as low as the career-low 7.1 percent walk rate Flaherty had in 2019. Flaherty’s 7.1 percentage point drop in walk rate is the largest among that same cohort of pitchers.

How has he done so? For starters, he’s throwing first-pitch strikes 62.4 percent of the time, his best rate outside a six-game debut in 2017. Like most pitchers, getting ahead in the count behooves Flaherty, who has a career .573 OPS against after he throws a first-pitch strike, compared to a .775 OPS when he falls behind 1-0.

That gap is even more pronounced this season -- opposing hitters have a .488 OPS against Flaherty after he throws a first-pitch strike, a stark contrast from the .751 OPS when he falls behind.

Another important element of Flaherty’s improved command is simply throwing fewer waste pitches -- essentially a non-competitive offering. Flaherty threw waste pitches 10.1 percent of the time from 2022-23, with both years representing career-high rates. In 2024, that figure has dropped to a career-low 7.3 percent.

There’s no doubt that Flaherty’s ability to pound the zone more is related to his strikeouts being at a career high level. Because the right-hander is getting ahead more often and throwing fewer non-competitive pitches, Flaherty has been able to do major damage with two strikes to finish off batters.

Put it all together, and Flaherty has never had this combination of bat-missing ability paired with elite command -- even during his best days in St. Louis. It's early, but there's optimism aplenty that Flaherty could be returning to a frontline pitcher.