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Tyler Anderson lost something

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The Mariners may have acquired another version of one of their starting pitchers

Seattle Mariners v Texas Rangers Photo by Ron Jenkins/Getty Images

Pitchers have used foreign substances for just about forever now. There’s historically been a gentlemen’s agreement amongst managers in which they do not request checks on opposing pitchers. Pitchers like foreign substances for obvious reasons: they, theoretically, allow pitchers to have a better grip on the ball. But also, it gives their pitches some extra movement. Hitters don’t exactly love that, but what many do like is that it gives pitchers greater control of their pitches, and makes hitters feel safer. With substances like Spider Tack gaining popularity, it’s gotten a bit out of hand, so Major League Baseball has actually starting policing the use of foreign substances. Some pitchers have been affected than others.

It’s not especially easy to pinpoint, but it feels appropriate to say that more than half of pitchers have benefited from sticky stuff (although the number of pitchers with statistically significant enhancements due to a foreign substance of some sort may be more than 60%). Pitchers with middling velocity and high spin who have utilized foreign substances seem to have been hit harder than most. And one of those pitchers appears to be Tyler Anderson.

I’ve always had something of an affinity for Anderson. He’s a lefty that, despite having middling velocity, has a pretty good fastball that gives hitters a lot of grief. In 2020, he ranked second of all starters in fastball CSW (called strikes plus whiffs) at 36.0% with a manageable (if not unsustainable) .359 xwOBAcon. In other words, he was an elite strike-thrower and limited hard-hit balls. For these reasons, Anderson is a pitcher who kept popping up for me as I perused different leaderboards over the offseason. But what he gained in 2020, he’s lost in 2021.

Consider Anderson’s fastball ride over the years, by month:

Anderson has always hung around nine inches of fastball ride, but in 2020, that figure leaped to over 10 inches. He maintained that fastball ride over the first two months of 2021, but then in June, his fastball ride plummeted back down to its previous levels. The reason for this may be obvious. It, perhaps, should be obvious. But if it’s not, I’ll spell it out for you.

Anderson’s 2021 spin rates, by game:

The dropoff in raw spin is stark. Through June 8th, Anderson’s average spin rate was 2405 rpm. Since then? His spin rate has plummeted to 2213 rpm. For starting pitchers, that’s a move from the 71st percentile to the 43rd percentile in spin rate. The dip in spin all but explains the drop in fastball ride.

Of course, I want to avoid assigning causation to correlation, but players were informed of the foreign substance memo before its actual release on June 15th. It was public as early as June 12th, but much earlier privately. So it stands to reason that Anderson may have sworn off of sticky stuff for the first time on June 9th — the first game his spin rate dipped — in order to get acclimated to the league’s enforcement of the rules that were set to take place on June 21st. As for how this affects Anderson on the whole, it’s...not pretty:

Anderson is a lot like Taijuan Walker in that he leans heavily on his fastball, but he doesn’t have much else. Walker can turn to his slider and splitter some, with mixed results, and Anderson has his cutter and changeup, which, while not exceptional, are more serviceable than Walker’s secondaries. That should help him ease the blow of his fastball potentially reverting back to its pre-2020 levels, but clearly, losing spin has affected him to the point that he’s gone from an above-average pitcher to a below-average one. At least by Stuff+.

I think the following numbers should corroborate the notion that Anderson has been affected by the foreign substance ban:

Tyler Anderson, Pre- and Post-Memo

Pre-memo 61.2 28.7 16.4
Post-memo 47.0 28.9 11.2

These are just a few things. They are not the only things, but they are things nonetheless. What this table tells us is that, between Anderson’s pre- and post-memo games, he’s shown a nearly-identical ability to throw strikes. Where he’s suffered is in his K-BB%. More specifically, his walk percentage has actually dropped by two percentage points, but his strikeout percentage has plummeted by a considerable 7.5%. That’s a helluva lot to lose, and it suggests more legitimate struggles for Anderson than it does statistical variation.

This is incredibly useful information! It can be simplified into this: on the whole, Anderson is not having any trouble throwing strikes. He’s been the same guy. But when he gets to two strikes, Anderson has had a tremendously difficult time putting hitters away — especially compared to the early season. He’s basically become a left-handed Chris Flexen. Flexen’s strikeout percentage before his August 2nd start was 15.5%. Anderson’s post-memo strikeout percentage? 15.5%.

The comparison isn’t only limited to this. Their repertoires have become increasingly similar over the past month and a half:

The y-axis changes between the two, so that’s annoying. But if you look closely, Anderson and Flexen both throw their fastballs with a little more than nine inches of ride, and their cutters and changeups are similar enough.

Where Anderson gets the nod is that his fastball has some arm-side movement, whereas Flexen’s is remarkably straight. Even with his losses in fastball ride, he’s shown the ability to continue to throw his fastball for strikes. That makes me feel a little better about his strikeouts coming back. That his fastball’s swinging-strike percentage has only dropped from 12.1% to 10.1% is encouraging too. But other indicators aren’t so promising.

The first is simple: he just...hasn’t thrown strikes in two-strike counts with his fastball. His two-strike fastball CSW has dropped from 21.0% to 11.3% since MLB released the foreign substance memo. The other thing is that he’s not locating it as well in such counts.

Anderson’s fastball location in two-strike counts, between time periods:

This is more subjective, but I’d argue that Anderson hasn’t been pitching to his best spots. Perhaps that’s purposeful! He might not have as much confidence in his fastball now. Or perhaps not! Maybe his fastball command isn’t quite there without some extra tack on the ball. It could even just be a bad stretch. Who’s to say?

In the end, I might bargain that Anderson isn’t likely to get his whiffs back. Not with his fastball. The best route may be to throw more cutters when he gets to two strikes, which should net him more strikes. The tradeoff is that his cutter allows more balls in play than his fastball, but if his fastball has truly taken a step back as a putaway pitch, then it’s a good compromise. Regardless of what Anderson ends up doing, we can probably feel comfortable saying that the early-season Anderson is long gone.

Odds are that Tyler Anderson truly is another version of Chris Flexen. That’s a comp that I don’t revel in for a pitcher who, at the beginning of the season, looked like an impact starting pitcher. But also, Flexen has been plenty effective, and Anderson should bolster a rotation that badly needs some stability. He’s only had one game as a Mariner, but so far, he’s been plenty decent. There will be some rough outings, but on the whole, it seems the Mariners did well to fill a hole in their roster.