With Soriano's injury - and the possibility that he's on the DL for an extended period of time - now's a good time to ask: If we end up going with Matt Murton in left for an extended period of time, how much worse off are we?

Let's start by talking about defense. Both of them are underrated defensive left fielders, but Soriano's greater speed and athleticism makes him a better defender than Murton. Sean Smith publishes defensive projections, and they say that Murton is a three run falloff from Soriano over a full season. I think that's a bit conservative - Sean is projecting Zone Rating, which doesn't measure arm strength. Soriano has an elite throwing arm for a left fielder, so let's go ahead and say 5 runs over a season.

Now, how about as hitters? For that we need projections of offense. There are a variety of projection systems available, and all of them seem to be pretty good at projecting established major leaguers. For the time being, let's use a composite of projection systems put out by Fantasy 411.

Let's look at the so-called "Sabermetric Triple Crown" of batting average, on base percentage and slugging. Murton projects to hit .293/.364/.464; Soriano projects to hit .280/.330/.534. Murton's a better OBP threat, and Soriano hits for better power. That said, the projection systems seem to be pegging Murton for a breakout power season this year. So the difference isn't as big as one might think.

Remember: one point of OBP is worth more than one point of slugging - you should multiply OBP by 1.8 to get them on roughly equal footing. But we can do one better than that - using linear weights, we can convert a player's offensive production to runs. Over a full season's play, we would expect there to be about three run's difference between them on offense.

So, three runs on offense, about eight runs on defense. Over a full season. Obviously if it's just a month or two you can prorate that out. If we use the Pythagorean Theorum, we see that it's somewhere between 10-11 runs to come up to a win's difference over a season. So the difference between the two players is one win. That's not a small difference, but nor is it an occasion for panic... yet.

(Implicitly ignored here are Soriano's impact on the basepaths - and to be quite frank, if he's injuring his legs this often, I don't see him stealing bases enough to matter in the analysis.)