When it comes time for free agency, most people tend to focus on offense. Production at the plate is the easiest thing to measure, and it typically has been valued more highly on the open market. In other words, the great hitters get the big bucks.
But if you just limit yourself to offensive analysis, you're getting a limited picture of a player's value. Take Prince Fielder and Albert Pujols, for example. They're the two biggest names on the free-agent market, and they both play first base. While you can argue that Fielder's offensive production could end up rivaling Pujols' over the life of their next contracts, there is no denying that Pujols is a far better defender and baserunner, and that's probably not going to change.
At Baseball Info Solutions we have a metric called total runs that sums each player's contributions on offense, defense (including an adjustment for the number of innings played and the relative difficulty of the position) and the basepaths.
Over the past six years, Pujols has outproduced Fielder at the plate, 787 runs to 706. The gap widens significantly when we consider their defensive abilities. We incorporate eight aspects of defensive play in our defensive runs saved metric (DRS), including a first baseman's ability to field ground balls and bunts. Fielder's minus-48 runs saved over the last six years make him one of weakest defenders at his position. Pujols, on the other hand, ranks as the game's top defensive first basemen with 76 runs saved since 2006. That's a difference of almost 20 runs per season, which according to the sabermetric rule of thumb that 10 runs equates to a win means that Pujols was worth two more wins than Fielder on defense alone.
The point is, a player's defense can make a huge difference and is one reason why Pujols might be undervalued, at least when compared to Fielder. Now, let's take a look at a few more players whose defense should greatly increase their free-agent value, as well as some guys whose defense should make buyers beware.
1. Alex Gonzalez, SS: While his offensive numbers are abysmal, his 31 DRS over the past two seasons make him one of the best defensive shortstops in baseball. With several ground ball pitchers on their staff, the Braves should make a strong push to re-sign the defensive whiz. The free-agent market is crowded with shortstops, and he could end up being a bargain.