The Value of Spring Training

(Editor's Note: Grant Bronsdon has joined the staff, bringing his journalistic acumen and statistical background to the staff. Also he goes to Yale, so now we have two Ivy Leaguers on staff. I am sorry. Welcome Grant!)

Seattle weather may not be very indicative of springtime, but watching the M’s every day on TV certainly is. And with spring comes a beautiful creation: Spring Training.

For those of you who haven’t been to Arizona in person to witness it, it truly is wonderful. Early-morning practices with 75-degree weather, the crisp sound of a bat smacking a ball, the oohs and ahhs that follow Robbie Cano or Nelson Cruz batting practice -- it’s all a wonderful sign that baseball is back.

But since it’s our first taste of baseball in months and months, we want to ascribe all sorts of meaning to what we see. We forget that this is a minuscule sample size in the middle of a time where players are trying to shake off the rust. It’s not easy to play 162 games over a six-month span, take four months off, and immediately get back to speed, whether you’re trying to hit a curveball or throw your best heater. And it’s for that reason that players’ stats might not mean much.

Look back at 2015, for example. In 21 games, Mike Zunino put up a .352/.435/.852 slash line with a team-best seven homers. Dustin Ackley hit .347 with more doubles than Cruz and Kyle Seager combined. Tyler Olson and Fernando Rodney combined for 21 scoreless innings -- and Olson finished with 15 strikeouts against zero walks.

So what should we know when looking at spring training stats? And what can we actually take from them?

1. Hitters do much, much better than pitchers.

The table below shows the Mariners’ collective slash lines in spring training and the regular season.

Though Safeco obviously accounts for some of the difference, it’s no accident that the M’s hit 38 points higher and slug a whopping 74 points higher in spring training. It’s easier to get back to game speed as a hitter, and pitchers don’t want to over-exert themselves in games that don’t matter.

It should also be mentioned, however, that this isn’t just due to hitters being more ready to go. Former Cardinals outfielder Chris Duncan wrote a piece last week where he says that pitchers "are often just trying to get their arms in shape, which means throwing more fastballs...Show up to a spring training game ready to hit the heater, and you’ll stand out at the plate."

Think of spring training as a sandbox, where pitchers are toddlers trying to build cool castles and hitters are the five-year-olds way too old to be playing with babies, smashing everything in their sight. But soon enough, they’ll be playing with kids their own size (or as recent years have demonstrated, they might become the toddlers in this analogy, swinging and missing at everything).

2. Sample sizes are just too small to mean much.

There are endless examples of players who excelled in the spring only to fall flat once April rolls around, or of players who can’t get anybody out in Arizona figuring out a curveball by the second or third week of the season.

This Fangraphs article from 2009 suggests that stats like on-base percentage and slugging percentage don’t stabilize until one reaches 500 plate appearances, and even rate stats like contact rate or strikeout rate don’t reach that mark until 100 and 150 PAs, respectively. In the past five years, the most plate appearances by any Mariners hitter is 82 in 2014 by Abraham Almonte, the one-time Center Fielder of the Future™.

That means that any statistics don’t have much predictive value as to a player’s talent, especially given the confounding factors of varying effort levels and pitchers’ desire to get their fastballs back in sync.

Needless to say, it seems pretty clear that were these numbers posted in the middle of June rather than in spring training, they wouldn’t be awarded extra significance.

So don’t get too excited at Daniel Robertson’s otherworldly .529 average in 17 at-bats, or Stefen Romero’s ridiculous 1.180 OPS. And, on the flip side, don’t be too worried by the 6.48 ERA posted by Taijuan Walker in 8.1 innings pitched.

3. If you can combine stats with scouting, surprise, you might have something!

The current state of the Mariners’ bullpen is, to put it lightly, not good. Injuries have ravaged the ‘pen, with recently-acquired relievers Ryan Cook and Evan Scribner either on the DL or likely to make it soon, and commercial favorite Charlie Furbush’s status for Opening Day is in question.

Justin De Fratus, released yesterday, allowed 10 baserunners in his six innings of work this spring, but even more worryingly, his velocity generally sat in the 89-91 MPH range, short of the target that the front office and coaching staff were looking for.

In De Fratus’ case, it seems obvious that the stats combined with his velo dropoff indicate he’s not the same hurler that posted a 157 ERA+ in 2014, and spring training provided an excellent chance to show that. If a guy like Mayckol Guaipe or Jonathan Aro were to add a new pitch and promptly stand out on the mound (note: these two have a combined ERA of 9.00), then those stats might be indicative of a larger change.

But fans should be careful about putting too much stock in spring training numbers, and using those numbers to determine which relievers should make the Opening Day roster could prove problematic.

No matter what, however, spring training stats do show us something pretty fantastic...

4. Baseball is back.

Sometimes, that’s all that matters.

Go M’s.