I don't feel like getting into the numbers yet. I just want to think about this theoretically for now. I had long held that pitchers shouldn't really be considered for the award of most valuable player. The standard logic behind that belief is that a pitcher only plays once every 5 days. While I don't find that argument to be as convincing as I used to, it still has some merit. But as with my other posts on this topic, it all depends on how you define value.
A pretty standard measure of value is how many runs you create or save, and then how that compares to the rest of the league. If you compare pitchers and position players without taking into account how often they appear a game there shouldn't be many reasons to say a position player is more valuable to a pitcher. The one thing I think you could say for the position player is that he is not only helping add runs, but with his defense he is helping prevent runs. And he is probably preventing more runs with his defense than a pitcher is with his offense.
But a position player's defense is dependent on the pitcher's performance. If you are an outfielder for the Braves and you have to play defense behind Derek Lowe and Tim Hudson 60 times a year you probably aren't going to get as many opportunities to prevent runs as those outfielders playing behind pitchers who induce fewer ground balls, and vice versa for infielders who would get more opportunities with ground ball pitchers. So without accounting for the frequency of appearances in games, we can probably give the slightest of edges to the position players in terms of their total contribution to value.
But before I get to the value a pitcher is adding I want to stay of the position player. While its true that he has the chance to add value in nearly every game a team plays, its not the case that he actually adds much value in every game. Take Albert Pujols as an example. I like to use him because I think most would agree that he is one of the best and most valuable players in the game. That makes it easier to conceptualize. Pujols can go 0-4 and not do anything defensively that an average defender couldn't do. What value did he add? The only place I can think off is his effect on the other batters in the lineup. Maybe Lance Berkman and Matt Holiday got better pitches because of Pujols' presence and they created runs from those pitches. That's something. But it was still up to Berkman and Holiday to follow through. So I'd say on Pujols' worst days he is only adding a little value.
Now let's look at a pitcher. When someone like Roy Halladay or Justin Verlander pitch they are adding a lot of value. They don't allow a lot of HRs, they strike out a lot of batters, and they pitch a lot of innings. During that game they pitch they are the player most responsible for preventing runs. Since that is half the equation to winning I'd say they are adding a lot of value by not giving up as many runs as nearly every other pitcher in the league. On an average day someone like Pujols is helping create a run or two. During that same game someone like Verlander or Halladay is helping prevent probably another run or two, maybe more depending on what the averages are. Like Pujols' effect on other players, the top pitchers are affecting other pitchers when they pitch well. They are keeping the bullpen from pitching more innings, which has the effect of having your better pitcher on the hill longer and having your best relievers available when your other starters aren't pitching well.
These indirect effects, Pujols on the rest of the lineup and the pitcher on the rest of the staff, are difficult to measure. So its difficult to say which one would bring more value. But I think I would give a slight edge to the position player on the basis of him having the effect more often. By the time you get to the 3rd and 4th starter in your rotation whatever effect your ace had is probably gone, or at least severely diminished. Meanwhile, even while Pujols was struggling early on this season, he was probably still positively affecting the rest of the lineup with his reputation every day.
It seems like so far I've convinced myself that on average a position player is a little more valuable than a pitcher. But the thing that I think makes it even closer is the concept behind WAR, wins above replacement. If you aren't familiar, WAR is trying to measure how many wins a player creates for his team compared to a replacement level player at his same position. There aren't many short stops that both hit and defend well. So when you find someone like A-Rod when he first came up that can do both of those things at a high level you have someone who has adds a lot of WAR. On the other hand there are generally a lot of first basemen who hit well and defend adequately. Since there are more of them available you aren't really adding much value to your team if you have an average first basemen compared to the rest of the league.
The reason I asked the question in the title is because pitchers like Verlander and Halladay are putting up some impressive WAR numbers. If they are adding a lot more wins that the average starting pitcher then they have a lot of value. I'm not sure what the actual numbers say about this season, but if Verlander and Halladay are pitching so much better than the rest of the league then I think they should be considered along side position players. If finding an elite pitcher is as hard as finding a SS like A-Rod then you are adding a lot of value to your team if you have one. So while on average a pitcher may not bring as much value in terms of creating and saving runs and thus winning games as a position player, he might be just as valuable to his team if he is pitching a lot better than the rest of the league.