The Mystery of Aaron Nola's 2019 Campaign

Philadelphia Phillies starting pitcher Aaron Nola is one of the top aces in fantasy baseball but has gotten off to a terribly disappointing start. Ben Rolfe dives into Nola's performances to determine what is wrong and whether he will show positive regression in 2019.

As we creep towards the end of the first month of the season, questions are starting to arise for fantasy baseball owners. Hitters are getting closer to having 100 plate appearances, and pitchers are now making their fourth starts of the season. We now have enough data where we can start looking for signs of concern among our star players.

Aaron Nola is one such player whose performances so far this season merit concern. Nola started strongly with a six-inning, one-run performance against the Braves. However, there were signs of concern even then, as he walked a major league career-high five batters. Since then he has given up 15 earned runs, allowing 19 hits and striking out 11 in 13 1/3 innings. The slight positive is that he has only walked six hitters in those 11 innings. However, he currently has a career-high 12.6% walk rate, and close to a career-low 21.8% strikeout rate.

The question is whether this start is a sign of a troublesome season or just an early blip. If it is the second of those, then he could be a buy-low right now, but if it is the first, then now might be one of the last chances to sell him for any sort of value. Let's take a look at some of the numbers behind the performances.

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Previous Seasons

We have never quite seen a start like this from Nola before. The table below outlines some of the top level numbers from his first four starts in the last four seasons.

A couple of things stand out immediately. First, outside of 2016, Nola has actually been a slow starter when it comes to strikeouts. However, in both 2017 and 2018, he ended the season striking out more than a batter per inning, with a K% over 25. It is also clear that his walk rate is higher this season than it has been in any of the others. However, in both 2017 and 2018, his walk rate in the first four starts was higher than it was over the course over the entire season (7.1 and 7.0% respectively), and slowly improved over the rest of the season.

Getting Hit Hard

The other major standouts this season are his ERA and HR/9. Both are way higher than any of his other season starts, and you would struggle to find many four-start stretches where he did this badly in his entire major league career. The reason for those inflated numbers can be found in his Statcast batted ball profile. Over the course of his major league career, Nola has a 4.8 Barrel%, 86.1 MPH Exit Velocity and a 7.7 degree Launch Angle.

This season he is allowing a 10.5 Barrel%, a 90.0 MPH Exit Velocity and a 9.3 degree Launch Angle. All of that translates into an xSLG and an xwOBA higher than anything we have seen in his major league career. Overall, his hard hit rate is nearly 10% higher right now than what we have seen in previous seasons.

Release Point

I think Nola's main issue right now his release point.

As of right now, his release point on all 4 of his pitches is higher than it was in 2018.

— Jack Fritz (@JackFritzWIP) April 16, 2019

A change in release point is not necessarily the reason for a major change in performance. However, it is a tangible change in the way he is pitching, and given that his velocity has not varied on any pitches, it is the only one we have right now.

His horizontal release point is closer to the middle of the mound than it has been the majority of his career. The chart above is broken down into monthly averages, and the change between March and April this season is interesting to observe. Let's take a look at how his vertical release point has varied.

Again, the vertical release point on all of his pitches this season are higher than they have been through large portions of his career. The Fourseam results especially are higher than most times in his career. All four of his pitches show the difference between March and April this season. Given that he produced a realtively solid performance in his March start, and has struggled in April it is worth taking note of. However, it is a small sample size, and there was a similar trend in change in release point at the start of last season.

If the trend continues between the different release point and the poor performances then it could be a real reason for concern. It will be interesting to see if the pattern changes in a similar way to what it did last season.

The Positives

As well as presenting the overriding negatives of what we have seen so far, I have also touched on some positive notes. Nola has been a slow starter in the past, and his release point changes we have seen this season mirror the pattern we saw at the start of last season. In 2018, Nola was one of the best pitchers in the game, so there is certainly hope for a turn-around.

Another massive positive is that some of Nola's underlying numbers suggest improvement is coming. His SIERA is down at 4.93, which is higher than his career average but much lower than his current ERA. Additionally, he currently owns a 27.8% HR/FB rate, which is double his career rate. The final element involves a new metric introduced by Alex Fast from Pitcher List, called strikes + whiffs (CSW). In that article, Fast demonstrated that CSW can be a predictor of future improvements, and that is a good thing for Nola this season. The league average for CSW is 28.7%, with anything over 30% being considered good. This season Nola has an average CSW of 30.1% through his first four starts. That number is slightly below his career average (30.55%) but it is in the right ballpark, and it is still in the good category.

Conclusion

I want to make it clear that I do have serious concerns about Nola. The concerns started when he walked five in his first start and they have then snowballed since then. After every start, I have had discussions with people about when we start taking serious notice of these numbers. Each start since that first start has just further validated my concerns and this last start finally meant the sample size was big enough to dig deeper.

The numbers above more than validate the concerns. There are clear indicators that Nola is struggling to open the season, with the walk rate, hard hit rate and the HR/9 being the biggest concern. Another element of concern is the strength of the NL East this season. The Braves, Nationals and Mets have all looked to have good offenses this season, and Nola is going to have to face those teams plenty this season.

However, there is also enough in the numbers above that give me hope he can turn this around. The similarities in release point and early season performances work in his favor, and the fact that his HR/FB rate is due for major regression. Additionally, his CSW rate shows encouragement that his strikeout rate will improve.

The intriguing thing here is that I could make the case for both selling Nola and buying low on him. If the walk rate and hard-hit rate are the issues, then this could just be the start of a season which spirals into further despair. However, if this is just another blip to start the season, then Nola could be a great value right now, especially if the Nola owner is experiencing a rough start to the season on the whole.

Judgement: Buy-Low

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