Which pitchers may be suffering most from MLB's foreign substance crackdown?

We're only halfway through the MLB season, but it's clear that this year will be defined by the league's crackdown on foreign substances. Since news leaked that MLB would start policing the use of substances during games, spin rates have plummeted across the majors - for some pitchers more than others.

This list isn't to state definitively that any of these pitchers were using foreign substances, but declining spin rates can often indicate a pitcher struggling to get a grip in a post-substance world. Here are three players who have been particularly lousy over the last month.

Gerrit Cole, Yankees

Cole could be considered the face of MLB's crusade against foreign substances, and his decline has been drastic. Through 11 starts in April and May, the Yankees ace owned a 1.78 ERA with 97 strikeouts through 70 2/3 innings. In six starts since, he's posted a 5.24 ERA with just 38 strikeouts in 34 1/3 innings, allowing at least two runs in all six appearances.

That stretch has coincided with a dramatic dip in the spin rate on all of Cole's primary pitches, dropping to levels he hasn't seen since he was with the Pirates in 2017. He can still pump heaters at 100 mph and is a good bet to eventually find his way in a post-substance world, but it's worth fading him until then.

Trevor Bauer, Dodgers

Perhaps no team has been hit harder by spin-rate dips than the Dodgers, and no Dodger has suffered more than Bauer, who has long been suspected of using substances to reignite his career in 2018. The reigning NL Cy Young winner had a 2.24 ERA entering June but simply hasn't been the same pitcher since.

The spin rate on his fastball dropped by 216 revolutions per minute from May to June and hasn't returned to old levels. For a pitcher as fastball-heavy as Bauer, that's a major problem. He's allowed at least nine base-runners in four of his last five starts, ceding a combined 14 runs (12 earned) in those four appearances.

Bauer's status moving forward is complicated by an investigation into assault allegations that have landed him on administrative leave. If he does return to the Dodgers' rotation, he could struggle to regain his old form, anyway.

Dylan Bundy, Angels

Bundy wasn't nearly as successful as the other two pitchers on this list through May, mustering a 6.49 ERA with an 0-6 record through his first 10 starts. Somehow, he's only been worse since then, recording fewer strikeouts (12) than earned runs (14) through 17 1/3 innings.

The Angels' struggling starter has also been among MLB's biggest decliners in spin rate for his fastball and curveball, which comprise nearly half of all pitches he's thrown this season. His lack of success on those two pitches is largely why he's made it out of the third inning just twice in his last six starts.

C Jackson Cowart is a sports betting writer at theScore. You can follow him on Twitter (@CJacksonCowart) or email him at [email protected].