Adley Rutschman's September Bounce Back Continues His Offensive Rollercoaster

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Boston Red Sox catcher Adley Rutschman had a hot start to the month of September, hitting three home runs in four games. Since then, Rutschman's batting average has tumbled, though he's maintained an excellent .500 slugging percentage.

His September output presents another shift in what has been an up and down year offensively. To paint the picture, a good starting place would be to look at his wRC+ in each month of the season.

March/April	May	June	July	August	September
200	82	97	106	41	106

As you can see, his season has not been consistent. Two caveats to point out here are the obvious trade from Baltimore to Boston, and his extensive time on the injured list. Anytime you have those factors at play, it has the chance to lead to inconsistency.

Still, in August, Rutschman had a slash line of .170/.254/.245 to go with an OPS of .500. Now in September, he has a .217/.250/.500 slash line and a .750 OPS. You can see that his average, slugging percentage, and OPS have increased sharply despite a drop in his on-base percentage.

Now, of course, you will expect some fluctuation from month to month throughout the course of the season. But what has led to this latest shift in the star backstop's performance at the plate?

Well, you've got a significant decline in walk rate (10.2% to 4.5%), which is owed to the fact that his swing rate has exploded (from 35.6% to 40.1%). He's simply taken on a more aggressive approach at the plate, which has created some fascinating discrepancies in his numbers.

Against fastballs he has a .318 average and a .727 SLG while averaging a 94 mph exit velocity on balls in play. Against breaking balls, however, he has a .200 average and a .600 SLG with his exit velocity ticking down to 83.5 MPH. The statistics plummet even further against off-speed pitches, to the point where he has essentially produced nothing against them in September.

When you get a hold of fastballs it can lead to extra bases, which it has in this case. When you can't produce well against an entire repertoire of pitches you will continue to see a lower batting average, low walk rate, and lower on-base percentage. There is also some luck leading to this output; his expected batting average and slugging percentage against fastballs this month are less impressive (.255 xBA and a .560 xSLG) that the actual results.

Essentially, even what he has been doing well is a little inflated.

All in all, Adley Rutschman has been better in September than any time since he arrived in Boston. That is a good sign, as the Red Sox will need him in the playoffs. But temper expectations for an October breakout—the underlying statistics are not indicative of a hitter who has fully found his stride at the plate.