Texas Rangers manager Ron Washington recently described plate patience as the ability to wait for good pitches to hit, particularly in a 0-0 count:

"Patience is that you have to have enough knowledge of what you’re doing that if you’re going to swing at the first pitch, you can’t be topping it, you can’t be rolling it, you can't be popping it up. You’ve got to turn somebody over.

You don't ground a first pitch to the third baseman. You don’t pop a first pitch to the second baseman. You don't chop a first pitch back to the pitcher. If you’re going to swing at a first pitch, you’ve got to center it. If you’re going to make an out, you’ve got to make a loud out."

Which Triple-A hitters are making the most noise when they swing at first pitches? Fortunately, we have the pitch-by-pitch data to answer that question. I counted lined drives and flyballs to the outfield as 'hard' hits, while every other batted ball in play is categorized as 'soft' contact. In this case, 'hard hit percentage' represents the proportion of first-pitch swings that result in hard hits. The average HH% among all Triple-A hitters is about 23%, and minor league veteran Mike Eylward has a sizable lead over any other hitter with a 58% rate (18 hard hits in 31 swings).
Here are the best performances by notable prospects with at least 75 plate appearances:

Player      Hard Soft SwingK Foul CalledK Ball    HH%
Matt Kemp     10    1     6     9      14   38  38.4%
Eric Duncan    6    2     6     4      26   46  33.3%
Wes Bankston  16    4    13    18      32   46  31.3%
Brandon  Moss 15    5    12    16      30   51  31.1%
Ryan Braun     8    5     2    11      23   52  30.8%
Junstin Huber 11    5    10    11      24   38  29.7%
Kevin Melillo  9    3    10     9      62   71  29.0%
Daric Barton  14   10     5    21      35   64  28.0%
Jeff Clement  14    9     6    21      32   53  28.0%
James Loney    6    3     4     9      58   71  27.3% 
Kurt Suzuki    7    3     5    13      55   59  25.0%  
Hunter Pence   9    2    12    13      23   30  25.0% 
Joey Votto    11    6     9    19      35   62  24.4%

Matt Kemp's placement at the top of this list is a pleasant surprise. Eighteen months ago, the Dodgers outfield prospect was a raw free-swinger at the plate.

And here are some prospects who are below-average, in ascending order of hard hit percentage:

Player      Hard Soft SwingK Foul CalledK Ball    HH%
Billy Butler   0    2      3    4      35   66   0.0%
Joel Guzman    3    8     10   15      29   36   8.3%
Joe Koshansky  3    6     11   12      53   49   9.4%
W. Balentien   6   10     16   19      43   54  11.8%
G. Kottaras    3    6      4    7      22   41  15.0% 
Yunel Escobar  7   12     10   14      29   54  16.3%
Andy LaRoche   6    9      9   10      23   49  17.5%
Eric Patterson 5    8      3   11      41   49  18.5%
Ian Stewart    8   11      8   16      38   52  18.6%
Rick Ankiel   10    7     15   20      21   54  19.2%
Adam Jones     8    8      9   14      42   56  20.5%
Brandon Wood   9    7     17    8      30   47  21.9%

Wow - Billy Butler just doesn't swing at first pitches. Some of the players on this list, including Butler and George Kottaras are here due to the small sample size and simply don't take many opportunities to hit the ball hard on a first pitch. Others, including Joel Guzman and Wladimit Balentien, are taking plenty of swings at first pitches and making poor contact or putting themselves behind in the count at alarmingly high rates.