Alex Rodriguez's injury-marred year contributed to a weak group of third basemen in 2011. Jim McIsaac/Getty Images

Are first basemen doing more to put runs on the board today than they did 10 years ago? How about 25 years ago? How do you make broad comparisons like this?

With any question like this you can get hung up on the differences between eras. Run-scoring environments are going to bounce around as a matter of course, and that’s before you get into the bump of the so-called "Steroids Era." If you were a fan just getting started in the late ’90s, chances are you might wind up with an inflated sense of what player performance is supposed to look like.

Happily, you can compare player performance within the context of their own season. Clay Davenport, an old colleague from Baseball Prospectus, cranks this data for every season. We can get a snapshot of where performance has gone at each position by using his Equivalent Average, or EqA. Equivalent Average isn’t the only stat you can employ; Clay scales production to batting average, with .260 defined as average.

With that in mind, let’s take a look at performances from the eight major positions over the past 25 years. We’ll start with the premium offensive positions, the four corners, from 1987 to the present:

Four-corner EqA performance at the plate, 1987-2011 ESPN.com

Keep in mind, .260 is average for every season, so the year-to-year variations are going to refer back to that baseline. We can already draw a few broad conclusions -- some of which are pretty much accepted wisdom, but some prove slightly surprising.

Runs come from first base. This might seem obvious, but that’s especially the case now. It hasn’t always been that way. As you can see from the chart, left and right fielders have sometimes approached the first basemen, but that usually coincides with bad years for first basemen. But these days, first base is the game’s premium offense position.

If you look back further, that picture gets a lot more complicated. During the ’70s, first, right and left were equally important offensive positions, and in 1982 the four corners and center field were separated by just eight points. That changed in the late ’80s, as the standard for production at first base now winds up north of a .280 EqA year after year.

This higher standard has survived two expansions and the steroid era. This year Mark Teixeira was below average despite hitting 39 homers. Admittedly, it was a down year for him: he posted a .281 EqA compared to an MLB average of .283. In contrast, in 1991 Carlos Quintana defined adequacy at first -- if you’re from outside Boston and have forgotten him entirely, it’s probably just as well, but he was a nice OBP guy without much power.

What does that mean today? Well, this goes a little bit towards what Dave Schoenfield was writing about as far as Albert Pujols ranking as the top player in the game for so long. It also means that while teams like the Rangers have been leaving runs on the table by playing Mitch Moreland, you can understand why the Red Sox traded for Adrian Gonzalez while the Angels landed Pujols. Credit the Rays for keeping up with the other big-money contenders by bringing Carlos Pena back (.292 last year).

Right field is where outfield stars play. This might take us back to the days of Babe Ruth or Hank Aaron as opposed to Ted Williams or Barry Bonds. While the averages for the two positions have balanced out over time, right field is the much stronger position these days. Some of that has is because of a matter of preference: Lance Berkman played right for the Cardinals not because he’s a good right fielder, but because he’d help them score a ton of runs. Jose Bautista might be a fantasy league’s perfect third baseman, but the Blue Jays keep bumping him back to the outfield. Add in breakthrough seasons for Mike Stanton and Matt Joyce and even nice bounce-backs from Justin Upton and Jeff Francoeur, and you wind up with the game’s reigning premium outfield slot.

Left field is down. Way down. As you can see, the last 25 years have been pretty up and down for the left-side corners. The average for left fielders in the era of division play is .277, but they haven’t reached that mark since 2004.

The sad state of left-field offensive production has already been debated plenty among statheads. Is it an affordable risk on offense at a time when teams are more defense-conscious than ever before? Or is it a case of reaping what you sow when you make a point putting guys like Juan Pierre in your everyday lineup? It might reflect an industry-wide choice to employ better defenders at the position, sacrificing some offense. But in other ways it might also reflect how left field has become almost a garbage-time position for teams that stow their backup center fielder or a sputtering veteran holdover. Teams now lack the roster space to platoon or mix and match on offense the way that they could before the seven-man bullpen became fashionable.

Whatever your take, offensive production from left fielders is down at its lowest point in 25 years, matching 1997 for punchlessness with a .268 EqA. That isn’t a coincidence; much like the present, 1997 featured a lot of transition in left fields around the majors, with guys like Gregg Jefferies, Wil Cordero and B.J. Surhoff playing their first full seasons in the outfield. Moises Alou got hurt (again), Bernard Gilkey’s career started imploding, and Greg Vaughn and Ron Gant had the worst years of their careers.

Fast-forward to the present, and you find your share of setback seasons (Carl Crawford and Delmon Young). You also see a lot of flat-out awful from self-inflicted bad ideas, like Raul Ibanez in the last year of his contract while Vernon Wells, Carlos Lee and Alfonso Soriano marked time on huge deals that won’t go away soon enough.

Against that, you’ve got the guys we might call sops to the speed-and-defense crowd, or what I think of as the next-gen Dave Collins solutions: Brett Gardner, Jose Tabata, Michael Brantley, Sam Fuld, Pierre and more. They range from useful OBP sources to significantly less so, but not one of them is going to be Tim Raines, let alone Crawford. Last year Gerardo Parra had the best season among this group (.280 EqA); he also stands to lose playing time in 2012 to Jason Kubel, a guy who’s a much more conventional corner-outfield selection.

Third Base is hurting. If you’re a student of baseball history, you already know that back in the Deadball Era second base was more of a high-offense position than the hot corner. That changed in the 1920s with the introduction of the livelier ball, but every once in a while you get a year where you’ve got a great group of second baseman and a weak crew of third-base vets. That was very much the case in the late ’80 and early ’90s (thanks in part to guys like Roberto Alomar, Ryne Sandberg, Robby Thompson, Lou Whitaker and Julio Franco), but after the Marlins-Rockies expansion in ’93 second base fell back again. But now we’re at this same point again, where third base has slipped behind second base, if only barely (.262 EqA to .261).

With the declining standards reflected by Scott Rolen getting named to an All-Star team despite a lousy season, finding merely competent options for third base isn’t as easy as it sounds. Alex Rodriguez and Chipper Jones certainly aren’t getting any younger.

You can hope this will change for the better with the arrivals of touted prospects like Brett Lawrie, Mike Moustakas and Lonnie Chisenhall, but we’ve also seen a few major third-base prospect flops: Pedro Alvarez or Andy LaRoche, anyone? That’s why journeymen like Casey Blake, Ryan Roberts or Jack Hannahan get opportunities to stick around.

If anything, the state of third base these days speaks volumes about the Tigers' decision to move Miguel Cabrera across to the diamond after signing Prince Fielder. As Mark Simon notes, the defensive penalty might be steep, but reviewing this data suggests that there's a major competitive advantage to be gained relative to the competition, because they're making room for two superstar bats in the lineup: Cabrera with his career .315 EqA, and Fielder with his .313. The Cardinals just ran up a flag after risking their defense at the corners with Berkman in right, so you can't blame the Tigers for trying to do likewise.

Tomorrow, we’ll look at the up-the-middle positions. If you’re one of those people who think finding good help at shortstop or catcher is hard to find these days, you might have a surprise to look forward to.

Christina Kahrl covers baseball for ESPN.com. You can follow her on Twitter.