Posted: Monday April 30, 2012 11:32AM ; Updated: Monday April 30, 2012 12:10PM
Cliff Corcoran

How good has Matt Kemp's April been? It's one of the best ever

Story Highlights

Matt Kemp is hitting .425 with 11 home runs and 24 RBIs entering play on Monday

In the past 39 seasons, ex-Giant Barry Bonds had the three best opening months

Kemp, last year's NL MVP runner-up, is the clear frontrunner for that award now

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Matt Kemp
A walk-off home run last Saturday was just one reason for Matt Kemp to smile this season.

Matt Kemp is off to an incredible start this season, hitting .425/.495/.888 with 11 home runs and 24 RBIs through Sunday. He's so hot that it has prompted the question as to whether or not Kemp is having the greatest April ever by a hitter, and if not, just where he ranks on the all-time list. (For a look at hot starts by pitchers see my story on Jered Weaver from a year ago.)

The easy answer is that Kemp isn't having the best April ever. With one game left to play, Kemp is going to fall far short of Barry Bonds' 2004 performance, even though Kemp's counting stats outpace those of Bonds, who had 10 home runs and 22 RBIs but but put up the absurd slash-line of .472/.696/1.132.

Unless he has a game for the ages in Denver on Monday, Kemp will also fall short of the April records for home runs (14 by Albert Pujols in 2006 and Alex Rodriguez in 2007) and RBIs (36 by Juan Gonzalez in 1998, including one on March 31 -- note that, where applicable, the April splits below include games played in March).

As for where his April will fall on the all-time list, that's a more difficult question to answer, and one I can only answer in part. To my knowledge, the best source for searchable monthly splits is David Pinto's Day By Day Database, and Pinto's data only goes back to 1974. So, short of searching every season of every player's career individually, we'll have to settle for a list that only covers 1974 to the present. Fortunately, that's the bulk of the data as, prior to the 1961 expansion, the major league season didn't start until late April, meaning Ted Williams and Babe Ruth and the like never played more than a dozen games before May.

The other challenge is how to quickly compare performances by different kinds of hitters over a nearly 40-year span during which the balance between hitting and pitching changed radically without the benefit of an easily-digested advanced statistic like Wins Above Replacement. I'll start with a favorite shortcut of mine called Gross Production Average (GPA). That stat goes a step further than OPS by combining on-base percentage and slugging percentage, the two most important hitting statistics, in a manner that gives proper weight to the former (avoiding outs is more important than hitting for extra bases, something GPA expresses by multiplying OBP by 1.8 before adding it to slugging), and then converts the result to a scale similar to traditional batting average (.260 is average, .300 is good, .200 is lousy, etc.).

Using 60 plate appearances as a minimum playing time requirement, I get a list, sorted by GPA, that looks like this (with GPA taken out an extra decimal place to break some of the ties that arise):

Barry Bonds 2004 .472 .696 1.132 .5962
Barry Bonds 2002 .376 .600 .828 .4770
Barry Bonds 1993 .431 .553 .889 .4711
Larry Walker 1997 .456 .538 .911 .4699
George Brett 1983 .460 .528 .921 .4679
Ron Cey 1977 .425 .543 .890 .4669
Jason Giambi 2006 .344 .554 .852 .4623
Albert Pujols 2006 .346 .509 .914 .4576
Otto Velez 1977 .442 .531 .865 .4552
Paul O'Neill 1994 .448 .543 .806 .4459
Matt Kemp 2012 .425 .495 .888 .4448
Barry Bonds 2007 .356 .536 .814 .4447
Jose Bautista 2011 .366 .532 .780 .4344
Ellis Burks 1994 .412 .472 .887 .4342

Bonds' 2004 performance, which contains the April records in all three slash stats in that period since 1974, is so far out in front that it should remain number one even after adjusting for the hitting-happy era in which it occurred, but it's pretty easy to move George Brett's performance hitting at Royals Stadium in 1983 ahead of Larry Walker's hitting in Coors Field in 1997. For some context, here's that same list with the league-wide GPA for April of the given year:

Player Year League GPA LgGPA
Barry Bonds 2004 NL .596 .259
Barry Bonds 2002 NL .477 .247
Barry Bonds 1993 NL .471 .239
Larry Walker 1997 NL .470 .245
George Brett 1983 AL .468 .246
Ron Cey 1977 NL .467 .245
Jason Giambi 2006 AL .462 .262
Albert Pujols 2006 NL .458 .257
Otto Velez 1977 AL .455 .250
Paul O'Neill 1994 AL .446 .267
Matt Kemp 2012 NL .445 .237
Barry Bonds 2007 NL .445 .249
Jose Bautista 2011 AL .434 .242
Ellis Burks 1994 NL .434 .254

A few things stand out there. Looking at the National League's 1997 splits, the ball didn't start jumping until May (.252 league GPA for that month), which puts Walker and Brett on surprisingly even footing above, at least before you factor in their ballparks. On the flip side, it's easy to forget that the addition of two expansion teams helped American League teams average an extra half a run per game in 1977 compared to 1976, or that the American League teams averaged 5.23 runs per game before the strike hit in 1994, a season in which the league as a whole hit .273/.349/.440 in April.

Most significantly for our purposes, however, is that Kemp's April has taken place in the toughest hitting environment for any of the 14 players above. If we take the player GPAs as a percentage of the league GPAs, a rough approximation of what OPS+ does so let's call it GPA+, we get a list that looks like this:

Player Year League GPA LgGPA GPA+
Barry Bonds 2004 NL .596 .259 230
Barry Bonds 1993 NL .471 .239 197
Barry Bonds 2002 NL .477 .247 193
Larry Walker 1997 NL .470 .245 192
Ron Cey 1977 NL .467 .245 191
George Brett 1983 AL .468 .246 190
Matt Kemp 2012 NL .445 .237 188
Otto Velez 1977 AL .455 .250 182
Jose Bautista 2011 AL .434 .242 180
Barry Bonds 2007 NL .445 .249 179
Albert Pujols 2006 NL .458 .257 178
Jason Giambi 2006 AL .462 .262 176
Ellis Burks 1994 NL .434 .254 171
Paul O'Neill 1994 AL .446 .267 167

Kemp moves up from 11th to seventh here. Also, note that the four Aprils above him -- Bonds in 2002, Walker in 1997, Ron Cey in 1977 and Brett in 1983 --are pretty tightly bunched from 190 to 193 percent of league GPA, just above Kemp's 188. Those performances are close enough that Kemp could catch or even pass them with a big day on Monday, though an 0-for-5 could similarly knock him down to 12th (a good illustration of the problem with small samples).

With that one game remaining, however, Kemp has clearly had one of the 10 most productive Aprils by any hitter in the last 39 major league seasons, which is impressive enough that his exact placement on that list shouldn't matter.
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