Are Maikel Franco and Aaron Altherr on the verge of breakout years?

It has been long-held conventional wisdom among a certain segment of this blog and the sabermetric community that spring training stats are worthless. If you dig deep into this blog's archive, you can find me writing about this topic over and over. My basic mantra - ignore spring training stats.

Or, as Joe Sheehan has put it, "Spring training stats are meaningless. It's the single most important thing to keep in mind every March."

However, there's reason to believe we were all wrong about this. In 2015, an editor at The Economist named Dan Rosenheck crunched the numbers and challenged this basic belief about spring stats. Actually, "challenged" is probably the wrong word. He destroyed it. As he said, "The claim that spring-training numbers are useless is wrong. Not a little bit wrong, not debatably wrong—demonstrably and conclusively wrong." His basic argument is that peripheral numbers, such as strikeout to walk ratio and flyball to groundball ratio, stabilize much earlier than average or on-base percentage do. Thus, the small sample size of spring training is, contrary to conventional stat nerd wisdom, useful information.

In particular, for hitters, he isolated three components that are most useful from spring training - isolated power, strikeout to walk ratio, and stolen base attempts. The latter is more about manager use or player comfort -- an uptick of stolen base attempts in spring very likely indicates the manager or the player (or both) want to steal more. According to Rosenheck, a change in the other two measures - ISO and K/BB - could indicate that the player's skill set has improved (or declined) and that spring training is just the first indication of such a change.

If Rosenheck is right, what does this mean for the Phillies' hitters this year? First, on the more simple stolen base measure, none of the Phillies has had a breakout spring with stolen base attempts, though Cesar Hernandez's 6 stolen bases against 24 hits and walks is an increase over last year's rate for him. He stole 17 bases last year against 227 hits and walks, which is a much lower rate than this spring. So, it's possible Hernandez will increase his stolen base attempts this regular season.

More interesting to me though is what the ISO and K/BB stats show. Here's the ISO chart for the Phils who made the team out of spring training and who are not appearing in the majors for the first time (sorry Andrew Knapp and Brock Stassi).

The three Phillies with the most improved isolated power numbers this spring compared to last year are Aaron Altherr (+.190), Maikel Franco (+.075), and Daniel Nava (+.058). I'm less impressed with Nava's improvement though, as his .127 ISO this spring is in keeping with his career .113 ISO (last year he posted .069 for his ISO, way off his career number). Both Altherr and Franco have improved this spring compared to their career and 2016 ISO numbers, signaling a possible power breakthrough for both of them.

On the flipside, five Phillies have had big decreases in their ISO this spring: Cameron Rupp (-.097), Cesar Hernandez (-.068), Michael Saunders (-.066), Freddy Galvis (-.057), and Andres Blanco (-.053).  Rupp and Hernandez have really struggled this spring, with ISO numbers way below both their career and 2016 numbers. Falling that far from their career ISO could mean they are just in slumps this spring. However, Saunders, Galvis, and Blanco all had upticks in 2016 compared to their career numbers, and their 2017 springs show their ISO just below their career numbers. It's possible these three are all regressing to their career power numbers compared to last year's blip.

How about patience at the plate?

Rupp and Nava have made the biggest strides this spring compared to last year, with both dropping their K/BB ratio by more than 2.5. Improved patience at the plate from both of them would be an outstanding development.

No one else has improved that drastically, but a bunch of other Phils have shown slight improvement compared to last year, and any improvement in this area of struggle for the team is welcome. Franco, Saunders, Hernandez, and Altherr have all knocked a bit off their ratio this spring. That Franco and Altherr are on this list is encouraging, as it means their improved power this spring has not come at the expense of their patience at the plate. That's a very encouraging sign.

Of most concern here is the trio of Galvis, Odubel Herrera, and Howie Kendrick. Both Kendrick (1.92) and Herrera (2.13) had decent K/BB ratios last year, both better than their career ratios. However, they've been terrible this spring. Herrera has a 7.00 ratio and Kendrick has a 14.

Even worse is Freddy Galvis. He also has a 14 ratio this spring, but that's coming off an outrageously bad 2016 when he had a 5.44 K/BB ratio (much worse than his terrible career 4.13). In other words, everything is going in the wrong direction for Galvis -- his ISO and K/BB this spring are possible indications that his 2017 is going to be a huge struggle.

Of course, there's no guarantee that any of these players' springs are going to be indications of what they are going to do this year. But, based on this new information about which spring training stats matter, there's reason to believe that Franco and Altherr could have big years in 2017, while Galvis could really deteriorate.