What do 75 PA's mean?

Lots of worrying in Braves nation lately.  Prado is off to a hot start with the bat, but everyone else not so much.  Cause for concern?  Lets take a look at the guys who are struggling a bit and see what we can uncover.  I'll frame the discussion as follows:

 50 PA: Swing %
100 PA: Contact Rate
150 PA: Strikeout Rate, Line Drive Rate, Pitches/PA
200 PA: Walk Rate, Groundball Rate, GB/FB
250 PA: Flyball Rate
300 PA: Home Run Rate, HR/FB
500 PA: OBP, SLG, OPS, 1B Rate, Popup Rate
550 PA: ISO

The above is the minimum PA's needed to have a reasonable shot at concluding anything about the particular value.  Worried about Player X's OPS?  If he hasn't had 500 PA's, then you are officially in the "small sample size" territory.  Below, I compare several players 2008 or 2009 season with 2010 and their career.  As you'll see, we can only extract meaningful information about their swinging habits, and we are getting close on contact.  The results of the PA's will need more time, but I'll compare them to the last healthy season and career to see if anything looks worrying.

Melky Cabrera

Results of PA's:

Plate Discipline:

Looking at Melky, I make the following observations.  First, he's swinging quite a bit less often than his career, both in and outside of the strike zone.  This fact is backed up by visual observation, where we see Melky taking lots of pitches and working the count.  Second, he's traded line drives for ground balls when he does make contact, which is likely what is driving his low BABIP vs. career.  Third, he's walking and striking out at rates higher than his career.  Interestingly, pitchers aren't throwing him anything good to hit, only 43.7% of pitches are in the strike zone.

My non-expert diagnosis:  I hope Melky's results are due to him still adjusting to NL pitchers he hasn't seen before.  He may be taking too many pitches early in the count, forcing him to be defensive with his swing once he gets to strike two.  His ISO and BABIP are unsustainably low vs. career averages, so I expect him to come around.  As Chipper would say -- its ok to swing at the first pitch if you can do something with it.  Being a little more aggressive earlier in the count may help him get some pitches he can do something with.  If he can turn those GB's back into LD's he'll improve.

Matt Diaz

Results of PA's:

Plate Discipline:

The "hittin' fool" probably needs to cool it a bit with the swinging.  He's swinging at an all time high of pitches outside the zone and swinging less at the good pitches -- both bad signs.  He's making good contact, but when he does hit the ball he's traded line drives for fly balls, which is hurting his BABIP vs. career.  What's not shown here, but worrying, is that Matt's K% has been steadily increasing over the years, from ~17% in 2006 to ~27% now. 

My non-expert diagnosis:  I am concerned a bit about Matt.  Most were calling for him to be a starter after he had career highs last year in BB%, ISO, BABIP, and HR/FB% especially.  To be honest, it looks like last year was about as good as Matt is going to get, and I suspect he is due for some regression this year.  The fact that his plate discipline is slowly eroding isn't going to help him get back to where he was last year.  I'd like to see Bobby play him only against LHP's until he can get things straightened out, but even then I think a repeat of last year is unlikely.

Troy Glaus

Results of PA's:

Plate Discipline:

Troy is swinging more often than he has in the past, and mostly at stuff that is outside of the zone.  Watching him, it looks like he is pressing and trying to hit everything out of the park.  He's a fairly extreme flyball hitter, and chasing all of those pitches out of the zone seems to be resulting in trading those long flies (HR's?) for ground balls, often DP's that piss everyone off.  Chasing bad pitches may also be affecting his BB%, which is not quite 1/2 his career average right now.  He's never been a high BABIP guy because of all of the FB's, but he is also due for things to start going his way on ball's in play.

My non-expert diagnosis:  If Troy can lay off the stuff out of the zone I think he'll be just fine.  He's seeing the same number of pitches in the zone and making the same contact he always has.  If he can get the plate discipline under control I don't see any reason he can't be the same Troy Glaus of 2008.

Nate McLouth

Results of PA's:

Plate Discipline:

It's hard to make out what's going on with Nate.  His BB% and K% are double his career average and he's hitting more LD's than ever but doesn't have the BABIP to show for it.  Looking at plate discipline, he's seeing some more pitches out of the zone, but not chasing them.  However, he seems to be taking strikes more often and making less contact.  Nate got fitted for contacts in the off season, so I wonder if he's still adjusting to how the ball looks now that his vision has been changed, hopefully for the better.

My non-expert diagnosis:  I'd like to see more data for Nate especially because it doesn't look like there's one thing in particular that is slowing him down.  Keeping his exposure to LHP's down should help, as he has struggled against them in his career.  I'm hopeful he'll come around, but worried his vision may still be affecting him in the batter's box.

In general, everyone is suffering from low BABIP vs. career, so even if everyone's plate discipline stays the same as now, I think the results will improve.  Troy and Matt need to work on laying off the bad pitches, and Melky may benefit from being a little more aggressive.  Nate's case is a bit of a head-scratcher (at least for me), so I'd like to see him keep at it.  Subjectively, his last few games seem like an improvement vs. spring training and his early April games, so he could already be getting on track as we speak.