Cubs Minor League Daily: Beware of Sample Sizes

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Cubs Minor League Daily: Beware of Sample Sizes

Cubs Minor Leagues and Prospects

willson contreras smokiesIf you look at the stats for Willson Contreras this morning, you are going to see some huge numbers in his slash line, starting with a batting average within shouting distance of .500. That’s right, I said batting average.

Entertaining though that line may be, it is essentially meaningless. Contreras is off to a very hot start, including three multi-hit games in his first six contests, but because the sample size is so small we can’t put much stock in those numbers. In fact, we’re three to four weeks away from being able to look at minor league number with any confidence at all.

In a nutshell, the problem has to do with how little data we are studying. We know baseball can be streaky, and we know that the best players in history have put up terrible numbers over very short stretches. We also know that the worst players in history probably looked awesome over very short stretches. Before we can be confident that the numbers we are seeing early in the season reflect reality and not just a random hot or cold streak, we need to be reasonably sure that sample size is large enough (that is, the numbers are calculated from enough plate appearances or innings pitched).

How large is large enough? Good question. It varies from stat to stat, and I’m not going to go into all those variations here.

A good rule of thumb, though, and the one I have been using for a couple of seasons, is to look for at least 100 PA for hitters or 25 IP for pitchers (sometimes less for relievers, depending on number of appearances). That 100 PA doesn’t have to start at the beginning of the season, either. I’ll often look at monthly numbers, or first vs second half numbers, and in many cases those figures are based on more than 100 PA. It isn’t a perfect benchmark, but it is a good rule of thumb.

And Contreras, unfortunately, is only about a quarter of the way to that 100 PA mark for the season. So, for now, we can’t view his awesome line with any confidence. We need another three or four weeks of games before we can get too excited.

If he is still hitting nearly .500 when he does hit the 100 PA threshold, though, I’m not sure we’ll be able to get excited enough.

Triple A: Iowa Cubs
New Orleans: 4, Iowa 2
The bullpen couldn’t hold onto this one.

Double A: Tennessee Smokies
Birmingham 5, Tennessee 4
Concepcion had another nice game in this one.

High A: Myrtle Beach Pelicans
Winston-Salem 4, Myrtle Beach 3
Thanks to the bullpen the Pelicans were able to mount a comeback, but it came up just short.

Low A: South Bend Cubs
South Bend 3, Bowling Green 2 in ten innings
Not just a walk off win, an extra inning bizarre walk off win (see below).

Other Notes

  • Paul Blackburn takes his super small sample size 1.80 ERA into tonight’s start for the Smokies.
  • Jonathan Martinez is probably not appreciated enough as a pitching prospect. He won’t turn 22 until June, and last season he enjoyed 116 pretty successful innings in High A. He should pitch his way up to Double A before season is out, but you can see him on for the Pelicans tonight.
  • The bottom of the tenth for the South Bend Cubs went like this: walk, walk, sacrifice bunt advancing both runners, walk, line out, hit by pitch for the game winning RBI. Why the odd line? The pitcher was Foo Fighters drummer catcher turned knuckleballer Taylor Hawkins. When you put a knuckleballer on the mound in extra innings in a tie game, sometimes that’s what happens.
  • The Iowa Cubs put up some really nice looking game summary graphics via Twitter. They maybe aren’t quite as awesome as the Enhanced Box Scores that are famous in these parts, but they are pretty sweet. The one for yesterday is below.


Author: Luke Blaize

Luke Blaize is the Minor League Editor at Bleacher Nation, and you can find him on Twitter at @ltblaize.