As it has become more apparent that the Twins are unlikely to add a number two hitter from the free agent pool, there has been some speculation that Joe Mauer would be moved into that role. Its hard for me to believe that Gardy would seriously consider that, but his alternatives right now are Hardy, Punto and Harris. Hardy has been a number two hitter most of his career, but he didn't really have the bat (or OBP) for it last year. My guess is he is the default, but it will depend on spring training performance once the coaching staff has had a good look at him. Both Punto and Harris have been tried in the number two spot. In some ways, Punto's OBP, speed and ability to work pitchers makes him the ideal number two guy. But it seems he is not comfortable in that role. Harris likewise has not really shown much there and lacks any of the normal skills you look for.
The result is that some in the blogsphere are speculating about moving Mauer up to number two. The common way that works seems to be that everyone else moves up a spot behind him so Morneau is the number three hitter and Kubel or Cuddyer are in the cleanup and number five spots. For purposes of this article, I am going to assume that is the way the rest of the order will go. Obviously there are other alternatives.
The primary argument for this idea is that Mauer will get more at bats and would get on base more often than anyone else. Part of this is the mistaken impression people have that how often a player gets on base is the most important factor in determining how often a player scores. But the actual data shows a wide variation in how often players score once they are on base. There are two factors in that. One is that some runners will advance themselves further than others, either by hitting for power or by better base running. The second factor, not surprisingly, is who is hitting behind them.
The argument against Mauer results from that second factor. Mauer's combination of average and power make him one of the Twins key players in bringing other runners around the bases. The number two and three hitters will have 162 plate appearances in the first inning, about one quarter of their total. If the guy batting second has an average OBP of .340, in the first inning Mauer will have 55 more runners on base when hitting third - 48+ runners with an OBP over .300. And the problem doesn't end with Mauer. Morneau batting third is also going to have fewer runners on base when he comes to bat than he would in the number 4 spot. The player in the cleanup role, whether Cuddyer or Kubel, may see more base runners since the cleanup hitter gets to hit in the first inning whenever even one of the first three guys gets on base. In the fifth spot and lower they will miss some of those opportunities.
The Twins number two hitters had 16 more plate appearances than the number three hitter over the course of last season, so Mauer would get on base about 6 more times in the number two spot compared to 5 times by an average number two hitter. You see similar result for Morneau, but the bulk of the plate appearances the alternative number two hitter would have had in that spot end up going to the 5th and 6th hitters - i.e. Delmon Young - assuming the alternative hitter does not appear in the order until after them.
So moving Mauer and Morneau to the number two and three spots shifts a lot of the RBI opportunities from Mauer and Morneau to Cuddyer, Kubel and Young. And, overall, you get only a handful of extra base runners. That tradeoff does not seem likely to improve the Twins run production.