With move to 1B, Mauer will have hard time earning rest of massive contract

Joe Mauer's days wearing the tools of ignorance have come to an end. (Jim Mone/AP) Earlier this week, the Twins announced that Joe Mauer, a three-time Gold

Joe Mauer's days wearing the tools of ignorance have come to an end. (Jim Mone/AP)

Earlier this week, the Twins announced that Joe Mauer, a three-time Gold Glove winner at catcher, will move out from behind the plate, becoming a full-time first baseman as of next season so as to avoid further concussion problems. It's a smart move in that it greatly increases the likelihood that Minnesota can keep one of the game's top hitters — and the franchise's marquee player — in the lineup with more frequency. While it will significantly reduce the risk of losing him for a long period of time due to additional injuries, or of having his career cut short, it will also make it harder for Mauer to live up to the remainder of his $184 million contract.

The 30-year-old six-time All-Star is certainly one of the best hitters in the majors at any position. He's the only catcher to win three batting titles, and among active players with at least 5,000 plate appearances, his .323 career batting average ranks first, two points higher than that of Miguel Cabrera and Albert Pujols. His .405 on-base percentage ranks fifth among that group, and although he's a bit light in the power department -- his .468 slugging percentage is 29th and he's only once hit more than 13 home runs in a season -- his 136 OPS+ is 11th.

For as great a hitter as he is, Mauer has had a hard time staying in the lineup, due to the position's general demands and a variety of injuries that have come with it. Only once has he caught more than 120 games (139 in 2008), and since winning the AL MVP award and the last of those three batting crowns in '09, he has averaged just 120 games and 516 plate appearances per year, including his time at DH and first base. Offseason knee surgery and bilateral leg weakness limited him to 82 games in 2011, while a foul-tip-induced concussion cut him off at 113 games this past season, none after Aug. 19. Mauer was still experiencing post-concussive problems — "sensitivity to light and noise, irritable moods and headaches" — into October, which led him to consult with physicians at the Mayo Clinic as well as team doctors about the increased risk of continuing as a catcher.

Sadly, the Twins are all too familiar with the toll of concussions. Justin Morneau was making a strong run at winning a second MVP award when a mid-2010 concussion cost him the remainder of the season. A career .286/.358/.511 hitter to that point, he has hit just .256/.319/.406 since, and while a slew of other injuries played a part in that decline, post-concussion syndrome still cost him a month more than a year after the injury.

As the repeated toll of concussions has become a billon-dollar problem for the NFL, awareness in baseball has been raised to the point that in 2011, MLB instituted a seven-day disabled list and a specific protocol for diagnosing and managing such injuries. Recent years have seen catchers such as Mike Matheny, Jason LaRue and Jorge Posada forced from behind the plate and/or into retirement not only by multiple concussions but by the sub-concussive blows that are an occupational hazard for a backstop via foul tips and incidental contact at the plate. Mauer is just the latest to move, and he won't be the last.

Mauer is three years into an eight-year extension that he signed in March 2010, one that guarantees him a flat $23 million in each year, with bonuses for various awards and honors. Thus far, he has delivered 11.3 WAR at a cost of $69 million, or about $6.1 million per win. Recent research by Baseball Prospectus' Russell Carleton (a former consultant for the Indians) has placed the going rate for a win among hitters in their seventh year and beyond (i.e., those with enough service time to be free agents) at $5.3 million*, so already Mauer has been under-producing relative to his salary. A closer look at his trajectory underscores the risk the small-market Twins face with his pact. When Mauer managed just 1.4 WAR in 2011, his deal looked like a disaster, and while his subsequent two seasons have been much better (4.4 and 5.4 WAR, respectively), 2012 was essentially a break-even, while this past year was a bit of a bargain even with the missed time.

Morneau's departure from the team has opened up Minnesota's first base job, so now the question is whether Mauer can produce enough value at the position to justify his contract. Based upon the positional adjustments built into Baseball-Reference.com's version of Wins Above Replacement, a defensively average catcher is worth an additional 10 runs to his team per year — the equivalent of an additional win beyond his offensive contribution — while a defensively average first baseman costs his team 10 runs. Here's B-Ref's position-by-position breakdown :

C: +10 runs

SS: +7.5 runs

2B: +3 runs

CF: +2.5 runs

3B: +2 runs

RF: -7.5 runs

LF: -7.5 runs

1B: -10 runs

DH: -15 runs

So all else being equal, Mauer would have to add 20 runs a year to his ledger on the offensive side to make up for the loss defensively. For his career excluding his abbreviated rookie season, Mauer has averaged 549 plate appearances per season. He's been 23.4 runs above average per 549 PA; extrapolating that to 650 PA, that's 27.8 runs above average, a gain of 4.4 runs. He's been a defensively average catcher during that time (-4 Defensive Runs Saved in 7,883 innings), so if he's a defensively average first baseman, that's a net of −15.6 runs per year. If he's a good first baseman, that might improve the ledger by 5-10 runs per year, so perhaps the net is −10 runs per year, the loss of about one additional win.

Of course, I haven't factored in aging patterns, and alas, even great players get old. Hitters age at different rates because their various skills -- power, plate discipline, contact ability, speed -- follow different aging patterns. The higher a player is above average, the farther he has to fall. Looking over the body of work on the subject and particularly that done by Jeff Zimmerman at FanGraphs, it appears that a great player might lose a total of 15-20 runs of offense from his age-31 to -35 seasons, which are the ones covered by the remaining years of Mauer's contract. Let's call it 20 runs, which equates to four per year, which is 0.4 wins.

Creating a model that factors in both Mauer's aging and the inflation of a value of a win from $5.2 million per year, you can see that Mauer's contract looks worse and worse as time goes on (all dollar figures in millions):

Year	Age	WAR	Salary	Mauer $/W	Market $/W	Surplus Value
2013	30	5.4	$23.0	$4.3	$5.3	$5.5
2014	31	4.0	$23.0	$5.8	$5.5	-$0.8
2015	32	3.6	$23.0	$6.4	$5.8	-$2.1
2016	33	3.2	$23.0	$7.2	$6.1	-$3.5
2017	34	2.8	$23.0	$8.2	$6.4	-$5.0
2018	35	2.4	$23.0	$9.6	$6.7	-$6.8
Total 2014-2018		16.0	115.0	$7.2		-$18.3

I've assumed that Mauer's value takes an instant one-win hit with the position change and loses an additional 0.4 wins per year on the offensive side due to aging. Meanwhile, the market value of a win increases by five percent per year. The result over the next five years is a total WAR of 16.0 at a cost of $115 million, or about $7.2 million per win, producing a total overpay of $18.2 million. That sounds like a truckload until you consider that the same math would show that Pujols, who was worth 1.5 WAR this year at a cost of $16 million, was thus overpaid by $8.1 million in a single year — and he still has eight years remaining on his contract. Also, this math means that Alex Rodriguez, who was worth 0.3 WAR and made $28 million in 2013, was overpaid by an astounding $26.4 million!

Of course, there are a lot of variables that go into the model above and changing any of them would produce significantly different amounts of overpay. If I assume Mauer loses 0.3 wins per year instead of 0.4 while inflation remains at five percent, the amount of overpay drops to $11.8 million. If instead I keep the aging pattern as in the model and boost inflation to seven percent, the overpayment figure would be $16.4 million. If I keep my original assumptions regarding aging and inflation but peg the value of a 2013 win at $6.0 million, the overpay during the remainder of the deal drops to $5.0 million. If I keep my original assumptions regarding inflation and the value of a win but assume Mauer will be merely average defensively, costing five more runs per year and thus resulting in 3.5 WAR for 2014, the overpay rises to $33.5 million. Do all of that while inflation instead creeps along at three percent, and the overpay rises to $35.1 million.

Roughly speaking, the shift of Mauer might result in an overpayment of five to 30 percent relative to the value he actually produces over the next five years. That's not a great deal, but balanced against the decrease in risk of him missing significant time due to further back, knee or concussion woes, or of having his career curtailed by same, it's an understandable bargain to strike, one that can be at least partially made up by Mauer's off-field value as a franchise icon around whom the team can build its marketing campaigns.

Looking at the issue from a completely different direction, one I undertook at Baseball Prospectus when the ink on Mauer's $184 million deal was still drying, I found that since the start of the expansion era (1961), the upper echelon of catchers produced roughly twice as much value before age 30 as after. That calculation included the position switches of players as diverse as Joe Torre, Ted Simmons, Craig Biggio, Brian Downing, Darren Daulton and Mickey Tettleton. Mauer produced 38.9 WAR through his age-29 season, and thus could be expected to produce 19.5 WAR the rest of his career. He's already banked 5.4 WAR at age 30, which means if he creates another 14.1 WAR over the next five years, he will be overpaid by $22.4 million. In other words, that finding fits within the estimates above, and it's reasonable to for Minnesota to hope that given Mauer's value at age 30 he'll hold on to it better than most of the other players in that pool.

I strongly suspect that the likelihood of a position switch is one that the Twins factored in when they hammered out Mauer's contract given the constant salary over time. In the absence of a strong catching prospect in their system, this move won't make turning their 96-loss team around a whole lot easier, and for a small-market team, his salary may remain a burden. Even so, this decreases the likelihood of an injury completely wiping out Mauer's value, and it's the right move for his own well-being.

*Originally, I had reported this figure as $5.2 million, when in fact it is $5.276 million, which rounds upwards to $5.3 million. I have revised all calculations connected to that figure.