Another Look at Mauer’s Power

Again looking at leaderboards, I noticed that only one of the top 10 hitters by batting average has fewer than 10 home runs; that would be your 2009 American League MVP, Joe Mauer.

Mauer is hitting .324 through 127 games and, barring a disaster to end the season, will finish as a 5-WAR player.  It’s a far cry from his 8-win 2009 season (which no one could reasonably expect him to repeat), and just looking at his lines across the two seasons, it’s not hard to see where the difference is.

2009 138 191 30 28 12.5% 12.0% 0.222 0.373 0.365 0.444 0.587 0.438 8
2010 127 155 41 8 11.3% 10.6% 0.140 0.345 0.324 0.400 0.463 0.370 4.8

The BABIP change almost entirely explains the batting average and OBP drop, but a lot of Mauer’s value in 2009 came from the 28 home runs.  He was third in slugging percentage in 2009 (behind only Albert Pujols and Prince Fielder), but this year is just 54th, between Victor Martinez and Gaby Sanchez.

Mauer hit nine home runs in the minor leagues (294 games), then hit 6, 9, 13, 7, and 9 home runs in his first five big league seasons, for a total of 44 home runs in 561 games.  Heading into 2009, the projection system PECOTA pegged Mauer for a 10 home run season with a .436 slugging percentage*.  Going into 2010, PECOTA predicted 19 home runs for Mauer and a .491 slugging percentage.  The five projection systems provided on FanGraphs had Mauer hitting 22, 18, 16, 21, and 19 home runs, with slugging percentages between .498 and .536.  So what happened?

Mauer’s plate discipline numbers remain virtually unchanged from 2009 to 2010, and only one number in his batted ball profile sticks out:

Season O-Swing% Z-Swing% Swing% O-Contact% Z-Contact% Contact% Zone% F-Strike% SwStr%
2009 20.4% 56.1% 37.0% 79.1% 91.1% 87.6% 46.5% 51.7% 4.3%
2010 24.4% 56.0% 39.4% 80.2% 96.2% 91.0% 47.6% 55.3% 3.3%
2009 1.62 22.6% 47.8% 29.5% 1.5% 20.4%
2010 1.56 24.2% 46.2% 29.6% 2.3% 6.3%

So he didn’t hit any more fly balls; he just hit more of those over the fence.  Since, for this study, I’m only really interested in the home run power, I checked Greg Rybarczyk’s HitTracker to get the details of Mauer’s 2009 and 2010 home runs.  From the website, here’s how it works:

Hit Tracker is a spreadsheet tool that takes as inputs atmospheric information and observation data, and gives as an output the true distance that the home run traveled, along with the initial speed of the hit off the bat and the precise angles at which the ball left the bat. It does this by creating as a starting point an initial “best-guess” three dimensional trajectory for the home run, and then modifying that trajectory, a little bit at a time, until the trajectory matches the observed data from the actual home run event.

With these data, Rybarczyk has categorized the home runs based on how far they go over the fence and, with the estimated trajectory, can determine how many parks that particular hit would have been a home run in.  He also categorizes home runs at “Just Enough,” “No Doubt,” and “Plenty.”  Again, Greg’s explanations:

“Just Enough” home run – Means the ball cleared the fence by less than 10 vertical feet, OR that it landed less than one fence height past the fence. These are the ones that barely made it over the fence.

“No Doubt” home run – Means the ball cleared the fence by at least 20 vertical feet AND landed at least 50 feet past the fence. These are the really deep blasts.

“Plenty” home run – Everything else, except for the 2 above Homerun types

Lucky Homer – A home run that would not have cleared the fence if it has been struck on a 70-degree, calm day.

With that in mind, here’s Mauer’s 2009 home run list:

Date Pitcher Team Ballpark Type/Luck True Distance # Park
9/19/2009 Verlander, Justin DET Metrodome ND 422 30
9/13/2009 Gonzalez, Carlos OAK Metrodome PL 382 30
8/31/2009 Floyd, Gavin CWS Metrodome ND 409 30
8/18/2009 Feldman, Scott TEX Ameriquest Field PL 433 30
8/18/2009 Feldman, Scott TEX Ameriquest Field PL 433 28
8/17/2009 Hunter, Tommy TEX Ameriquest Field JE 372 26
8/15/2009 Sipp, Tony CLE Metrodome JE 417 24
8/13/2009 Meche, Gil KC Metrodome PL 414 29
8/8/2009 Verlander, Justin DET Comerica Park PL 366 27
8/7/2009 Galarraga, Armando DET Comerica Park JE 381 26
7/31/2009 Santana, Ervin LAA Metrodome JE 407 18
7/24/2009 Lackey, John LAA Angels Stadium PL 420 29
7/24/2009 Lackey, John LAA Angels Stadium JE 416 21
7/8/2009 Coke, Phil NYY Metrodome JE 369 16
6/20/2009 Moehler, Brian HOU Metrodome PL 420 30
6/12/2009 Wells, Randy CHC Wrigley Field PL 388 12
6/2/2009 Huff, David CLE Metrodome JE 358 13
5/25/2009 Papelbon, Jonathan BOS Metrodome PL 417 24
5/24/2009 Bush, Dave MIL Metrodome ND 421 30
5/23/2009 Looper, Braden MIL Metrodome JE 361 21
5/21/2009 Gobble, Jimmy CWS U.S. Cellular Field ND 385 22
5/19/2009 Buehrle, Mark CWS U.S. Cellular Field PL 378 22
5/16/2009 Chamberlain, Joba NYY New Yankee Stadium JE 418 22
5/15/2009 Coke, Phil NYY New Yankee Stadium PL 426 27
5/12/2009 Galarraga, Armando DET Metrodome JE 360 9
5/9/2009 Hernandez, Felix SEA Metrodome PL 392 29
5/8/2009 Jakubauskas, Chris SEA Metrodome JE 381 20
5/1/2009 Ponson, Sidney KC Metrodome PL 390 27

Of Mauer’s four home runs, only four were No Doubts, 13 were Plentys and 11 were Just Enoughs.  Three of the four No Doubts would have made it out of all 30 parks.  Only three of the Plentys and none of the Just Enoughs had enough to get out of all 30.  The average for each type was 28, 26, and 20 for No Doubts, Plentys, and Just Enoughs, respectively.  Now for 2010:

Date Pitcher Team Ballpark Type/Luck True Distance # Park
8/18/2010 Floyd, Gavin CWS Target Field JE 367 11
8/10/2010 Garcia, Freddy CWS U.S. Cellular Field PL 412 27
7/26/2010 Marte, Victor KC Kauffman Stadium JE 384 30
7/23/2010 Guthrie, Jeremy BAL Camden Yards PL 411 5
7/6/2010 Tallet, Brian TOR Rogers Centre JE 415 25
6/19/2010 Lidge, Brad PHI Citizens Bank Park JE 419 24
5/14/2010 Burnett, A.J. NYY New Yankee Stadium JE 402 30
4/6/2010 Saunders, Joe LAA Angels Stadium JE/L 409 4

A different story.  No No Doubts, only two Plentys, and six Just Enoughs, including three that would have made it out of less than a dozen ballparks.  There was only home run that would have made it out of so few ballparks in 2009.  Thanks to this great tool, we can also see where Mauer’s home runs ended up in each season.



Only nine of Mauer’s 28 home runs in 2009 were hit to the right side of second base; only three to six more could be classified as left-center, meaning that Mauer hit 13 (or 16) home runs to left field in 2009.  Just looking at the chart, a lot of those look like Just Enoughs, traveling between 350 and 380 feet.  All of Mauer’s pulled home runs traveled at least 400 feet.  It doesn’t seem to me like Mauer did anything differently in 2009 than he did previously or that he’s doing now.  He has always hit the ball to all fields, and in 2009, some of those fly balls to left field found their way into the seats.  Joe Mauer doesn’t have to hit 25 to 30 home runs to be a valuable player; that he did it in 2009 (along with hitting .365 while playing catcher) made him an easy choice for MVP.  Given the extension he got before the 2010 season, he won’t have that long of a career as a backstop; the Twins are going to make sure he hits for as long as he can.

This article was originally published on Knuckleballs, written by Dan Hennessey.

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no mention of park change? Didn’t he move to a bigger home park?


Speaking purely anecdotally, I remember Mauer hitting quite a few line drive type home runs to left field in the Dome last year. That kind of batted ball has seemed much less likely to go out of the park at Target Field this year.

ESPN’s Park Factors has Target field tied with Safeco for being the hardest park to hit home runs in (the number is .637, but I’m not exactly sure what it means). The home run factor for the Dome last year was 1.111, a favorable number for the hitter. I think there is a very good chance that Target field has had a huge impact on Mauer’s power this year.


Very nice. I’d be interested to see data on ball speed off the bat, which seems to be the only explanation – aside from the switch from the Metrodome to Target field as mentioned above – for a shift in HR/FB rate … outside of random noise, of course.


Obviously he is off the roids now…

It would be interesting to see how many balls he has hit off of the wall this year compared to last year. I’d in 2009 his doubles off the wall were turning into HR’s. He does have 11 more doubles in 2010 than in 2009.

Mike Green
Mike Green

Mauer’s home/away splits from 2009 to 2010 suggest that park effects are the most important factor. His away line has not changed substantially.


It is not as if Mauer’s power has become all but extinct – he has been hitting plenty of XBH in 2010. It is just a matter of whether his batted fly balls have left the park or not.

In 2009, they did. In 2010, they haven’t.

Quite simple, really.


Adohaj, speed off the bat averaged 102.2 this year, 102.6 last year. Distance this year has averaged 401.9, last year it was 397.7. All of this is according to Doesn’t look significant to me but who knows.


Having watched a great many of Mauer’s games the last few years, I submit a large portion of the drop in HRs for 2010 is the Target Field effect. Balls hit to the gaps tend to die unless truly pured, or you catch a lucky break with the swirling winds.

Mauer’s “just enough” HR in Yankee Stadium was a line drive over the left center field fence, that hit a railing in the aisle between sections. I’m surprised to see it referred to as “just enough.”

It’s not just Mauer that’s seen a drop, Cuddyer has gone from 32 in 2009 to 14 so far in 2010, Kubel 28 to 19, and even Span has had several balls most thought were gone not even hit the wall.

It’s the stadium as much as anything.


Mauer did admit to changing his approach at the plate last year – agressively trying to drive fastballs more often when he’s ahead in the count. How much impact that had is hard to say, but the conclusion that he did nothing different lat year than he did in previous years.

And have seen analysis from Twins bloggers that indicate (at least in the first half of the season) that indicated pitchers were adjusting by throwing him less fastballs when behind in the count.

But it’s clear the main issue is TF. His HR/FB% away this year is 10.7%. At Target Field it’s 1.7%. Both numbers are still well off last year’s rates, though, but in neutral parks he’s probably more of a 15-20 HR a year guy right now, not a sub-10 guy.

Morneau also suffered a MAJOR power drop at home this year – 38 AB/HR in 2010 vs. 19 AB/HR in 2009.



3 of his 9 homeruns (33%) when he was ahead in the count. His SLG (ahead/even/behind) was .551/.500/.385

17 of 28 (60%)

It looks like he was doing proportionally better in 2009 when ahead in the count. Whether this is because of pitcher adjustment, I’m not sure.