Aaron Nola: Worlds of Potential

Heading into the 2017 season, we here at Crashburn Alley strive to update you on a specific storyline regarding many of the returning staples from last season’s roster. Today is starting pitcher Aaron Nola.

A lot of what I said in my season preview for Jerad Eickhoff could be repeated for Aaron Nola. He’s got the stellar curveball, so-so fastball, and not good changeup. Nola both strikes out and walks slightly more hitters, which gives both players near identical career K/BB rates just below 4.00. However, Nola has allowed more home runs per fly ball, and he just came off a season with a near-5 ERA.

Based on that paragraph alone, you might conclude that Eickhoff is the better pitcher right now, and you might be right, but that misses three important pieces of information about Nola that set him apart from his rotation-mate:

  • Due to his sinking fastball, Nola had a 55% ground ball rate (GB%) in 2016, compared to Eickhoff’s 41%. The league average is about 45%.
  • Nola had a strand rate (LOB%) of just 60% last year, while Eickhoff’s 76% was just above the league average of 73%.
  • Nola has dealt with injuries that may have affected his effectiveness.

When it comes to balls in play, ground balls are the ideal outcome for a pitcher. They very rarely go for extra bases (ISO: 0.020), and therefore, they have the lowest wOBA against of the three batted ball types (just .220). And even this undersells the value of ground balls, because they’re the batted ball type that is most likely to produce a double play. Nola’s ground ball rate ranked eighth in baseball last year among pitchers who threw at least 100 innings last year.

As for strand rate, I’ll let the FanGraphs Glossary take this one:

Most pitchers have LOB%s around league average (which is approximately 70-72%, depending upon the season), and pitchers that deviate from that average tend to see their numbers regress towards average in the future. In other words, if you see a pitcher with a 60 LOB%, they are letting lots of runners score so their ERA will be high, but the odds are that they will strand more runners in the future and lower their ERA.FanGraphs Glossary

In other, other words, strand rate is a fluky statistic that is likely to revert to league average for Nola this year. That doesn’t tell the whole story, as there are some extenuating circumstances that cause certain pitchers to struggle with runners on base. For instance, some pitchers may struggle out of the stretch with mechanics, but Nola hasn’t shown that consistently, as his strand rates in the minors and in his first MLB season have never been below 77%.

All of this is not to denigrate Eickhoff, as he’s shown himself to be an above average big league starter. It’s just to say that Nola has all the tools to be even better than his fellow righty, and he pitched at an ace level through the beginning of June. However, in his last 8 starts, Nola struggled mightily and was eventually shut down for the season with an elbow injury. It’s possible that he was pitching through injury towards the end of the season, and the statistics bear that out, though it should be noted that both Nola and the Phillies denied that he had been pitching through pain. Compare his first 12 starts with his last 8:

Whether or not he was injured, it’s clear that Aaron Nola has the potential to be a top-of-the-rotation starter. No qualified starters produced a K% greater than 27% and a BB% below 5% in 2016. The only pitcher to do that over 80 or more innings is Clayton Kershaw. And only three qualified starters produced a K-BB% of greater than the 22.4% Nola accrued in his first 12 starts: the late Jose Fernandez (26.9%), Max Scherzer (25.3%), and Noah Syndergaard (23.5%). Oh, and Nola had a higher GB% than all three of them. Simply put, for his first 12 starts last season, Nola was one of the best pitchers in baseball. The only thing separating him from the upper echelon of MLB pitchers is his durability.

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