Is MLB's Offensive Resurgence Connected to Looming Crackdown on Sticky Stuff?
Jonathan Daniel/Getty Images  Roughly three months after it first warned teams that it would be cracking down on pitchers using foreign substances, Major League Baseball now seems ready to actually back up its talk with action. In what may or may not be a related story, the league's hitters are starting to heat up after a historically slow start to the season. Regarding the aforementioned crackdown, Ken Rosenthal of The Athletic reported that umpires will start checking pitchers for foreign substances during commercial breaks and even during innings if they deem it appropriate. If a pitcher is using anything, he'll be ejected from the game, and his equipment will be confiscated. For MLB, arguably the biggest potential benefit of ramping up its policing of foreign substances is that it could mean the end of ongoing embarrassment. Though New York Yankees ace Gerrit Cole (see here) and Los Angeles Dodgers ace Trevor Bauer (here) are the most notable pitchers to get caught up in sticky-stuff suspicion, it's become clear throughout 2021 that the conspiracy goes well beyond them. Of course, the other potential benefit is that fewer pitchers doctoring baseballs might level out a playing field that's become skewed heavily in their favor. It's no secret, after all, that hitters are working on their lowest batting average since the league hit just .237 during the "Year of the Pitcher" in 1968. But especially after a high-scoring weekend that featured a whopping 119 home runsincluding eight by the Toronto Blue Jays alone on Sundayit's hard not to notice that the latter issue is already on its way to being resolved. Video Play Button Videos you might like  Hitters' Historic Struggle May Be Over  Though hitters didn't exactly have it easy even before 2021, it seemed early on like they were in for a challenge unlike any other this season. To wit, the league-wide .232 batting average in April was the lowest monthly mark since the batsmen of 1968 hit .230 in April and then .229 in May. Even after upping their average to .239 in May, the hitters of 2021 were still on track for a new all-time-low .236 average. That's no longer the case now, however, because a .247 average thus far in June has pushed the league's mark up to what would be a futility-dodging mark of .238. Data courtesy of Baseball Reference  Granted, June isn't over yet. And if you're thinking that it's nothing out of the ordinary for hitters to perform better in June than in April or May, well, you're not wrong. The conventional wisdom holds that hitters warm up with the weather, and the numbers typically bear that out. It's not often, however, that hitters see a 15-point increase in their batting average from April to June. Such a swing has happened only four times in the last 70 seasons, including just twice since 1987. As for what, exactly, is driving this improvement, one factor is that balls are flying over the fence more frequently in June than they did in April. In the latter, 3.1 percent of all plate appearances resulted in a home run. In the former, it's 3.4 percent. Yet there's been an even bigger shift in the league's strikeout rate, which has gone from 24.4 percent in April to 24.0 percent in May to 23.4 percent in June. On Foreign Substances and Spin Rate  If anyone's curious as to why MLB is only now getting interested in enforcing rules that have been on its books for a long, long time, it has to do with how pitchers using foreign substances used to be no big deal. It was a commonplace practice that even hitters were generally indifferent about. What's changed in recent years, however, is the why of pitchers applying sticky stuff to the ball. Whereas the pitchers of yesteryear may have merely wanted a better grip for the sake of their control, the pitchers of today typically want a better grip for the sake of their stuff. Pitches get nastier the more they spin, and the word is out now that the right sticky stuff can do wonders for a pitcher's spin rate. It's therefore hard not to be suspicious of how the league's average spin rate has risen on an annual basis since 2015. And since high-spin pitches miss bats at a higher rate and are generally harder to hit than low-spin pitches, it's likewise hard not to be outraged on behalf of all of MLB's hitters. Now that everyone has all the background, here's how the league's spin rate has progressed in 2021:  Up in April. Up again in May. But now, down in June. Since spin goes as velocity goesi.e., the faster the pitch, the more it spinsthis could potentially be explained by a sudden drop in velocity in the month of June. But that particular trendline is actually heading in the opposite direction. The average pitch in April was 88.7 mph. It's now 89.0 mph in June. Unsurprisingly, the downward shift in the league's spin rate has been good for the league's hitters. Though they should be credited for improving against high-spin pitches (i.e., at least 2,500 revolutions per minute) as the season has moved along, they're seeing fewer of those now and feasting even more so on the extra low-spin pitches:  Data courtesy of Baseball Savant  In spite of all these numbers, the hard part is proving that they're the direct result of fewer pitchers using sticky stuff when they're on the mound. Statcast can and does track many things, but it can't tell us who's using pine tar, Spider Tack or whatever. And yet it doesn't seem like a coincidence that the league's diminished spin rate and improved offense are so neatly encapsulated in the month of June. It was in late May, after all, that veteran umpire Joe West got the ball rolling on tougher enforcement by scrutinizing the dirty caps of relievers Giovanny Gallegos (see here) and Craig Kimbrel (here). Between those incidents and MLB's looming crackdown, it's fair to say that pitchers are on notice. Likewise, it's fair to observe that they're acting like it. And now for the part where the tinfoil hats come off for the sake of acknowledging other contributing factors to the league's recent offensive surge. For starters, it never did make much sense that hitters were batting just .283 even when they put the ball in play back in April. The league-wide batting average on balls in play is typically much closer to .300, so it's little wonder that the BABIP shot up to .292 in May and is now at .296 in June. That's a sensible regression. It's also no accident that balls have been flying over the fence more frequently this month. In both April and May, fly balls of at least 95 mph averaged exactly 365 feet in distance. So far in June, those same fly balls are now averaging 369 feet. That's solid evidence that even the new deadened ball still travels better in warm weather. And as you might have noticed, the weather in the last few weeks has been very warm. Still, even if the league's improving offensive numbers can't be tied specifically to the sticky-stuff situation, it's at least interesting that it's only taken a couple of weeks for some smoke to emerge in that particular neck of the woods. Once MLB's crackdown is in full force, the resulting fire could be impossible to ignore. Stats courtesy of Baseball Reference, FanGraphs and Baseball Savant and are current through Sunday's games.