Chicago Cubs left-hander Justin Steele turned in arguably the best start of his career on Sunday, albeit in a loss against the Milwaukee Brewers. Steele delivered six shutout innings, holding the Brewers to two hits and a walk. He struck out nine batters, and he set a new career-high with a 76 Game Score, a Bill James invention that attempts to gauge start quality by adding or subtracting points based on a pitcher's stat line.
At minimum, Steele's outing continued his recent hot streak. He hasn't allowed more than two earned runs in a start since July 13, when he surrendered all of three. Moreover, he's now allowed one earned run or fewer in seven of his last nine efforts. Over that stretch, he's averaged more than five innings per start while compiling a 1.47 ERA and a 3.47 strikeout-to-walk ratio. (For posterity's sake, we will note that he's more prone to allowing unearned runs by virtue of being a groundball pitcher.)
Steele's pitching is one reason why the Cubs have been on a second-half surge. They've won 17 of their 28 games since the All-Star break, including 11 of their 19 games in August. The Cubs won't factor into the postseason race -- even now, they remain well below .500, at 52-68 -- but the development of Steele (among others) is a welcomed one for a franchise that has produced few homegrown pitchers since the days of Kerry Wood, Mark Prior, and Carlos Zambrano.
Indeed, the Theo Epstein era was successful in many respects, but drafting and developing arms could not be counted among the wins. Steele would appear to be an unlikely candidate to help turn the tide -- Baseball America ranked him as the organization's 22nd-best prospect entering 2021 -- yet it's hard to knock his efforts.
Below, we've highlighted three changes that help explain Steele's accent this season.
1. New fastball
One of the most glaring changes Steele has made is with his fastball. He's not throwing it harder (his average four-seamer is actually coming in a mile per hour slower), but he is throwing it with a new shape. Last season, Steele's four-seam fastball averaged about two inches of horizontal break to his arm side; this year, he's averaging 1.5 inches of horizontal break toward his glove side. In layman's terms, his four-seamer is now serving as more of a cutter:
2021
93.2 mph
2.1 inches
15.4 inches
2022
92.2 mph
-1.5 inches
19.3 inches
Steele's four-seamer benefits from the concept of seam-shifted wake, too. (That's a fancy way of saying the pitch moves differently than you'd expect based on its spin.) He has the second-highest deviation from spin-based movement to observed movement among left-handed pitchers, trailing only Baltimore's Nick Vespi.
It should be noted that Steele's fastball results have by and large not improved with his shift to a new movement profile. He has allowed fewer home runs and a lower slugging percentage with his four-seamer, but his batting average against is up and he's generating fewer whiffs. Still, it's important to consider how each pitch plays within the context of an arsenal, and it's possible that Steele's new-look heater has made his slider, his top secondary pitch, more effective in ways we can't capture.
There's reason to believe Steele thinks so, based on his pitch utilization.
2. Altered pitch mix
Steele split last season between the rotation and the bullpen at the big-league level. In doing so, he threw four pitches at least 10 percent of the time: his four-seamer and slider, as well as his sinker and curveball. (For those wondering, he does have a changeup, but he's thrown two for every 100 pitches thus far in his big-league career.)
Steele has veered closer to being a two-pitch pitcher this year. His four-seamer usage rate is up from 45 percent to 57 percent, and he's spamming his slider nearly twice as often, from 16 percent to 30 percent. Steele has made further alterations to his pitch mix in-season: his share of four-seamers and sliders has increased by more than nine percentage points since the break, as compared to his first-half starts.
Whereas Steele's fastball has suffered through worse results despite its new shape, his slider has enjoyed greater effectiveness while being used at a higher usage level. Batters are hitting .130 against the pitch and have whiffed 32.5 percent of the time; last season, for reference, they hit .182 against it with a 29.7 percent whiff rate. That's a promising sign for Steele and, again, it may hint at there being an improved interplay between his new four-seamer and his slider.
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Speaking of hard-to-measure improvements.
3. Better control
One of the most fundamental ways for a pitcher to take a step forward is to improve their ability to locate. Better control and command can go a long way in enhancing a pitcher's repertoire, allowing offerings to play above their stuff level. Making gains in those respects is easier said than done, obviously, but Steele does appear to have tightened his geography this season based on several statistical indicators.
For starters, Steele has reduced his walk rate. Last season, he issued a free pass to more than 10 percent of the batters he faced; this year, that percentage is down to 9.4 percent. Additionally, he's throwing more strikes (63.3 percent versus 61.7 percent) and his pitch-tracking data indicates a greater share of his pitches have been either in the zone or on the edges as compared to last season.
No one is going to confuse Steele for prime Cliff Lee -- his walk rate is still one of the 10 highest among pitchers with 100-plus innings -- but even small improvements can lead to a better overall package. For evidence of that, just take a look at Steele's recent stretch, and his emergence as a legitimate rotation option heading forward.