Carson Smith Has Hit a Wall

There are a lot of things that have gone wrong during the 2015 season, but none has been more frustrating than the painful demise of the Mariners’ bullpen. You’re familiar with the story by now; the bullpen led all of baseball in ERA and xFIP last year and was surprisingly healthy. This year has been the complete opposite. The Mariners’ relief corps is 24^th in ERA and 27^th in park adjusted FIP and a few key members from last year have spent significant time in the minors.

One of the lone bright spots amid this sea of misery has been the emergence of Carson Smith. During the first half of the season, he was one of the best relief pitchers in all of baseball. In 38 appearances before the All-Star break, Smith had a pitcher slash line of 1.73/1.98/1.97 and his 7.83 K/BB ratio was second best in all of baseball. He supplanted Fernando Rodney as the closer by June and accumulated six saves.

Alarmingly, something has happened to Smith after the All-Star break. In 15 appearances since the All-Star Game, his pitcher slash line has ballooned to 5.79/3.03/3.55 and his K/BB ratio has fallen all the way to 1.82.

We’re working with such small sample sizes that there’s very little we can conclusively determine. Carson Smith’s first half numbers were so good that we probably should have expected some regression, but his struggles in the second half can’t be explained away by such simple means. Over on FanGraphs, Jeff Zimmerman has completed some excellent research into injuries and the indicators that may point to potential problems. That research will inform much of my analysis.

The Breaking Point

On July 21, Smith earned a four-out save in Detroit. He threw 21 pitches, walked one and struck out one. It was his second appearance after the All-Star break and he was pitching on two days of rest. Over the next six days he would make four more relief appearances, including three straight days between July 23 and July 25. He threw a total of 55 pitches in those four relief appearances, walked five, struck out three, and gave up three runs.

The Warning Signs

During this four game stretch, Carson’s average fastball velocity dropped more than a mile per hour and just 30% of his pitches found the strike zone. His velocity would rebound in his next appearance but it’s been on a steady downward trend since the end of July. Observe:

The red arrow points to the game on July 21. Carson’s average fastball velocity fluctuated wildly in early August and then fell sharply after his appearance against Baltimore on August 11. It was at the lowest point of the season in his next appearance, his 35 pitch adventure in Boston.

Smith has also struggled to throw strikes since July 21. His Zone% during the first half of the season was 48.5% but that’s dropped to just over 40% in the second half. His walk rate has spiked to 16.7% as a result.

His mechanics look like they might be out of whack as well. His vertical release point has slowly fallen over the course of the summer and it’s now an inch and a half lower than it was earlier this season.

That may not seem like much, but it’s significant enough to warrant some concern. A pitcher who is pitching through an injury might change their throwing mechanics to mitigate the pain of a violent throwing motion. Of course, if you examine that graph, Smith’s release point has varied throughout the season. It could be just noise in the data.

Here’s all the relevant data from these two periods:

Date	Zone%	FB velo	FB V release	SL velo
Pre-7/21	48.5%	93.9 mph	5.48 ft	85.7 mph
Post-7/21	40.3%	92.8 mph	5.35 ft	85.2 mph
Difference	-8.2%	-1.1 mph	-0.13 ft	-0.5 mph

Conclusions

A loss of velocity and trouble pitching in the strike zone are the two primary indicators of pitcher injury. July 21 might be an arbitrary date to pick as the breaking point; most pitching injuries aren’t so cut and dry. It’s usually a long, slow process of wear and tear before something gives out. The true breaking point could have come at any point during the second half of the season, or even earlier.

I’ve focused mainly on Carson’s fastball so far. His slider looks to be mostly unchanged. He is throwing that pitch more often in the second half (40% sliders in the first half, 50% after) which could also lead to greater injury risk.

Even if Smith isn’t injured, it’s clear that his stuff has suffered lately. He’s just an inning shy of his total from last year and he’s on pace to throw the most innings in his professional career. If he is fatigued, that could lead to increased risk of injury, especially if he has more outings like the one he had in Boston.

The Mariners have a valuable asset in Carson Smith. He’s shown he’s capable of putting up incredible numbers out of the bullpen and he’s just 25-years-old. If he is pitching through an injury, or even if he’s only fatigued, the Mariners need to start monitoring his work load and start thinking about when to shut him down. His long term value far outweighs the small amount of value he’d bring to the club for the remaining month and a half of the season.