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Run Differential, With and Without Joe Mauer

"The inflammation [is] in the SI joint and they are going just change the medicine and see where we go from there. Change the type of medicine he’s taking ... go with something more aggressive."

That's Ron Gardenhire, talking about Joe Mauer's back inflammation.  Right now it sounds like there's no relation to the kidney operation of three months ago, but that in itself will be no help to the Twins offense if Mauer needs to take some time off.

If, like me, you have absolutely no idea what the sacroiliac joint is (or what it does), a quick internet search tells me this:

  • There is a left and a right sacroiliac joint, located at the base of the spine.
  • Inflammation causes pain in the lower back, buttocks (that's for you girls, Joe Mauer's buttocks) and thighs.  Clearly this would be an issue for a catcher.


Cmathewson broached the topic of Mauer's back on Tuesday, and there's a lot of good discussion in the comments thread.  Be sure to take a look.  My question is a bit different, as you can probably guess.  It's not about who will necessarily sit in for Joe, but rather what kind of an effect will his absense have on run production?

In 2008 the Twins scored 829 runs, good enough for third in the American League.  Using Baseball Musing's lineup analysis tool, the standard Twins lineup last season (Span, Casilla, Mauer, Morneau, Kubel, Young, Buscher/Harris, Punto, Gomez) would have scored 5.089 runs per game...or, 824 runs.  Not that you should believe everything Baseball Musings tells you, but for the simplicity of the experiment we're running that's an incredibly accurate prediction.  Which means, naturally, I'm happy to use the tool going forward.

Here are the two lineups we'll be using to predict run production in 2009:

Split Lineup #1
(With Joe)
Lineup #2
(Without Joe)
1 Span Span
2 Casilla Casilla
3 Mauer Cuddyer
4 Morneau Morneau
5 Cuddyer Kubel
6 Kubel Crede
7 Crede Redmond
8 Punto Punto
9 Gomez Gomez

There are enough lineup variables even having Mauer in the batting order, much less deciphering how it'll look without him, but this is what we're going with.  Using these lineups, we'll run two experiments with each:  the first will use career bests by the standard of OPS+ (hitting .500 in four at-bats in a rookie season doesn't count), the second will use career averages.

Career Bests
Lineup #1:  5.567 RPG / 902 RPY
Lineup #2:  5.286 RPG / 856 RPY

This is the top end of the spectrum, because if every single player in this lineup sets record highs in their offensive performances this season then the Twins should score at least this many runs.  By 2008's standards, Lineup #1 would have been the American League's best offense by one run.  Lineup #2 still would have been good enough for second place.  Either way, this team would win plenty of games on offensive merits alone.

Career Averages
Lineup #1:  4.887 RPG / 792 RPY
Lineup #2:  4.663 RPG / 755 RPY

These projections are a bit more realistic.  Everything being even (which it never is on the field, no matter how simple it looks on paper), if not one player hits below his career line then this is what Minnesota's offense would look like.  Lineup #1 would come in right in the middle of the pack, seventh in the American League.  Lineup #2 would be 11th.

Using the 745 runs the Twins allowed in 2008 as a basis for the formula, here are Minnesota's pythagorean win-loss records for our four outcomes:

Lineup #1 (Career Best):  95 - 67
Lineup #2 (Career Best):  91 - 71
Lineup #1 (Career Averages):  86 - 76
Lineup #2 (Career Averages):  82 - 80

The reality is that to finish with 90 wins (or more), the Twins will need to see some improvements in their defense and pitching, because it seems that unless everyone has a breakout season the offense won't be able to manage that win total it on its own.

With Joe Mauer, it looks like the Twins are roughly an 86-win team.  With improvements on defense and pitching, even removing 17 runs from 2008, the pythagorean record still awards the team just 87 wins.  That's borderline for playoff contention, even in a weak division.

Without Mauer, there would be no October.  That's made very clear.  On a team like the one fielded by the Twins, with very few offensive stars, losing one of the club's two best hitters would have a drastic effect on the long-term fortunes of the team.  It's not like Joe is worth 50 runs on his own, but between driving in runners on base and getting driven in after he's earned his way on, the Twins have a drastically different (and definitely more potent) batting order when he's penciled in.

Thankfully, Joe isn't going to be out for the entire season.  Chances are he'll still be able to join the team sometime in April, and as long as he's healthy the offense has a pretty decent shot at finishing in the top half of the league in scoring.