Mike Napoli's improved health could mean a big season

The Boston Red Sox look poised to retake their place atop the standings in the American League East. A busy offseason has netted them a suite of significant players: Hanley Ramirez, Pablo Sandoval, Ryan Hanigan, Rick Porcello, Justin Masterson, and Wade Miley. This group should compliment the existing roster and help push the Red Sox back into playoff contention in 2015. However, as with any team, the new acquisitions are not the whole story. To be a formidable team the Red Sox will also need strong contributions from roster holdovers like Dustin Pedroia, David Ortiz and Mike Napoli. For me, Napoli represents an interesting example of a player who should have a positive change in his numbers from 2014.

Napoli tends to be a three true outcome (TTO) guy. Over the last four seasons, 46% of his plate appearances have ended in a walk, strikeout or home run. For a reference point, the often-touted kings of the three true outcomes, Adam Dunn and Rob Deer, each had career marks of 49%. So Napoli fits the TTO mold. Focusing on Napoli's two seasons with the Red Sox (which will be the primary focus of this work) finds Napoli's TTO rate at 49% in 2013, and 46% in 2014.

Last season was a slight down year for Napoli in Boston. His fWAR came down from 3.9 in 2013 to 2.5 in 2014. While his offensive numbers were similar, 129 wRC+ in 2013 and 124 wRC+ in 2014, he got to those points on different paths. Below is a table with his isolated power and plate discipline numbers for 2013 and 2014 (all relevant to those cited TTO rates):

Season	PA	ISO	BB%	K%
2013	578	0.223	12.6	32.4
2014	500	0.171	15.6	26.6

You can see that his power took a big step down in 2014. His ISO of .171 was actually the first sub-.200 season he has posted since 2007 (in 263 PA). This change in power numbers was not a result of exchanging power for a higher batting average. While his power numbers saw a decline, his ability to get on-base increased. In 2014 he walked more and struck out less often than he did in 2013. How did this change come about? One indication from his plate discipline numbers is that he swung less often:

Season	Swing%	O-Swing%	Z-Swing%
2013	42.2	26.0	61.9
2014	40.4	24.0	61.0
Career	42.0	24.6	62.4

Digging a little deeper shows that Napoli most dramatically changed his approach on breaking and offspeed pitches (especially between 2013 and 2014).

2013 is an outlier for swinging at offspeed stuff, but getting this rate back down to his typical level and laying off breaking stuff (that may end up outside the strike zone) resulted in more disciplined plate appearances for Big Nap in 2014.

This provides at least a partial explanation for Napoli's change in BB% and K% from 2013 to 2014, but what about his power numbers? Perhaps the simplest answer is that in 2014 Napoli was a ground ball (GB) hitter. In every season prior to 2014 his ground ball-to-fly ball ratio (GB/FB) was less than 1 (mean ratio = ~0.84). But in 2014 this ratio jumped to 1.26. Rather than stroking line drives (LD) and FB he was hitting GB:

Season	LD	GB	FB
2013	24.4	36.9	38.8
2014	18.9	45.3	35.8
Career	19.3	38.1	42.6

Groundballs tend to result in poorer outcomes for a batter than do line drives and flyballs, and this is especially true for someone who is not exactly fleet of foot like Napoli. To some extent, it was hitting a lot more groundballs that sunk Napoli's power numbers. That, and when he hit a fly ball he was not doing as much damage as he had in previous seasons; for example, his 16.7 HR/FB rate was his lowest rate since 2009.

We have clear evidence of specific changes in Napoli's performance between 2013 and 2014, but we can still ask: what drove the change? It could just be random variation and we could anticipate that in 2015 his numbers will bounce back to career levels (adjusting for aging). Or it could be suggested that he worked hard with the Red Sox hitting coaches to develop a new way to approach his plate appearances and therefore hard work explains his change in performance. However, I don't think the changes seen in Napoli's plate discipline and power were entirely random variation, nor were they all about a conscious change in plate discipline. Rather, I think the changes in Napoli's performance came about because he was tired.

This offseason it came to light that Napoli suffers with sleep apnea, and that in 2014 it was really bad. Initial concerns about Napoli's health were hip related, so much so that his first contract with the Red Sox was incentive-laden. His hip has not given him the trouble, it has been the thing many of us take for granted: sleeping. Now, I am not that kind of doctor, but sleep apnea is a disorder wherein breathing during sleep is atypical. There are pauses in breathing that disrupt the sleep cycle, causing the person to wake up multiple times throughout the night. This means that the person is not resting properly, and as a result will generally be more tired during the day. Being tired directly impacts alertness and the ability to perform cognitive tasks (for example, those involved in playing baseball). Hitting a baseball is consistently ranked as one of the hardest things to do in professional sports. It requires an incredible focus of attention, and rapid decision-making. The batter has to determine if the incoming pitch will be in (or around) the strike zone, and then whether it is a good idea to attempt to hit it. The batter can make the decision by guessing the pitch characteristics before it is thrown, relying on differences in the pitcher's release point, and/or reading the spin on the ball as it is in flight. Integrating this decision making process with faster-than-typical-people reaction time abilities, and great arm strength is what allows batters to actually complete this ridiculously difficult task.

There is little doubt that the process of anticipating pitches and trying to hit them would be affected if the batter was consistently fatigued. To continue oversimplifying things, it would get a lot harder. With fatigue, reaction times would be slower, and pattern recognition (guessing pitch sequences and tracking ball spin) would be more error-prone. The end result of this process taking longer, and/or having more error could be indecision, hesitation and the bat staying on the shoulder. Milliseconds matter in baseball. This is why pitchers who throw hard are treasured. Throwing the ball with great velocity takes away decision-making time from the batter.

The relevance of all of this for examining Mike Napoli's performance is that given his condition we can assume he was likely fatigued much of time in 2014 (reportedly more so than in previous seasons). If this was 1984, a bowl of ‘greenies' might be available in the clubhouse to help combat his fatigue. Instead Napoli had to deal with it himself. In some cases he would skip batting practice so that he could take a nap. We also know that Napoli swung less in 2014, and saw a greater proportion of pitches outside the strike zone than is typical for him (career: 49.7%; 2014: 52.2%). The combination of these events would likely result in the observed change in plate discipline numbers discussed above. So we can ask, was his decrease in swing% because his batting eye suddenly got better in his age-32 season? Or was it that his typical decision making process was slowed by fatigue? Obviously, we cannot know for sure. But, a consideration of the change in batted ball outcomes could be taken as additional evidence that it was actually more related to a change in his decision-making and reaction time than an improved batting eye. As noted, in 2014 he hit many more groundballs than usual. Subtle changes in reaction time and ability to make swing adjustments during a swing would affect the outcome and quality of contact.

While I have primarily focused on certain aspects of Napoli's hitting, his defensive and base running numbers were also lower in 2014 than in previous seasons. The decline in these numbers contributed to his lower fWAR. I will not delve too far into the exact numbers, as they tend to have more season-to-season variation than the hitting statistics cited, but it seems reasonable that these areas of his game would also have been impacted by fatigue.

The good news for Napoli, and in turn Red Sox fans, is that he had surgery to correct his sleep apnea. So he should be getting better rest. Early reports are that he is, and feels like he has significantly more energy throughout the day. What this all means for projecting his 2015 season remains unclear. A rested Napoli, full of energy, might get back to swinging more often. As a result his plate discipline numbers could return to previous levels, which would be fine if it means he is making better contact and hitting for more power. As it stands today, Steamer projects Big Nap for 2.5 fWAR, which is in line with his 2014 season. Given his expected bounce back in health, I think it is fair to expect him to exceed that projection. If he does, it will likely get labeled as a contract year push, but I will be there to suggest that any positive change in 2015 has more to do with improved health than it does with contract chasing. Regardless, Napoli certainly has a key role in the outcome of the Red Sox season. If he ends up drunk and shirtless walking around the streets of Boston in October (again), things likely went well.

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All statistics courtesy of FanGraphs and Brooks-Baseball.

Chris Teeter is a featured writer and editor at Beyond the Box Score. You can follow him on Twitter at @c_mcgeets.