One of my favorite toys here on FanGraphs is the Past Calendar Year split. I like the rolling 365 day line, as it gives us a good view of what a player (or team) has done in the equivalent of the most recent full season they have played. Because the MLB season started earlier this year, the totals don’t work out to exactly 162 games, but it’s close enough to give you the right idea at least.

Just for fun, here are the win-loss records for every team in the American League, using the data from the past calendar year filter.

Team Wins Losses Winning % Athletics 108 60 0.643 Yankees 97 70 0.581 Tigers 96 70 0.578 Rangers 96 70 0.578 Orioles 96 72 0.571 Rays 90 77 0.539 Angels 84 82 0.506 White Sox 80 85 0.485 Red Sox 81 87 0.482 Royals 78 89 0.467 Mariners 77 90 0.461 Twins 71 94 0.430 Blue Jays 70 95 0.424 Indians 68 100 0.405 Astros 52 117 0.308

While the St. Louis Cardinals have steamrolled baseball for the first couple of months of 2013, the A’s have been winning games at an equivalent clip to STL for the past year. A .643 winning percentage over 168 games is an impressive accomplishment, especially considering that the A’s are still overshadowed by the Rangers, Tigers, Yankees, and Red Sox when people talk about AL contenders. However, none of those teams have even been with 10 games of Oakland over the last year.

Once again, Billy Beane, David Forst, Farhan Zaidi, and company have built a terrific baseball team despite limited financial resources. Unlike the A’s from the Moneyball era as chronicled by Michael Lewis, there really are no home grown “stars” that you can point to as the reason for the team’s success. This team was built almost entirely by acquiring undervalued assets via trade or free agency.

The team’s best player over the last year has been Coco Crisp, who has put together a pretty remarkable stretch of baseball in the last 365 days. Since June 13th of 2012, Crisp has played in 132 games, racked up 590 plate appearances, and has hit .293/.368/.494, good for a .370 wOBA while playing half his games in a pretty extreme pitcher’s park. As a center fielder who also happens to be one of the game’s premier baserunners, the total package adds up to +5.4 WAR, and that’s with UZR rating his defense as slightly below average.

This is not a fielding driven valuation. The only players with significant CF time who have posted a higher wRC+ than Crisp’s 138 over that stretch are Mike Trout (159), Andrew McCutchen (147), and Shin-Soo Choo (145), and those numbers don’t even account for Crisp’s baserunning. We’ve got him adding an extra 7.8 runs of value, so when you factor in that value, Crisp has been nearly Choo’s offensive equal while adding significantly more value with the glove. On a per plate appearance basis, Crisp has basically been the offensive equal of Andrew McCutchen.

Before the start of last season, the A’s signed Crisp to a two year, $14 million contract with a team option for a third season. He’s making $7 million per year to put up the kinds of numbers that are worthy of a down-ballot MVP vote. Crisp has been paid about $2 million per win since signing with the A’s; that’s a remarkable steal given the going rates for talent.

Right behind Crisp is Josh Donaldson, who has racked up +4.8 WAR in the last 365 days, and remarkably, that only covers 114 games and 477 plate appearances. Donaldson has actually hit even better than Crisp, putting up a .375 wOBA/141 wRC+, which is basically a dead on match for Evan Longoria’s .376 wOBA/143 wRC+ over the same time period. Toss in his positive defense at third base, and Donaldson has played at an elite level ever since getting recalled from Triple-A last summer.

And Donaldson is one of those classic Beane acquisitions, as he was the fourth prospect in the deal that sent Rich Harden to the Cubs in 2008. At the time of the trade, Donaldson was a 22-year-old hitting .217/.276/.349 in the low-A Midwest League. He’d been taken 48th overall in the 2007 draft, showing some offensive ability in college, but this wasn’t a highly valued prospect who has finally lived up to the hype. Donaldson looked like a bust very early on and then improved enough to make himself a fringe prospect who might have a future as a bench guy. Moved out from behind the plate and with a new approach to hitting, the A’s have helped turn Donaldson into a quality third baseman.

After Donaldson is the one Oakland hitter who hasn’t struggled to get recognition for his success. Yoenis Cespedes was something of a splashy acquisition for Oakland, as they gave him a four year, $36 million deal as a free agent before the start of last season. The A’s aren’t generally known as big spenders on veteran international free agents, but they landed Cespedes by giving him a shorter deal that would allow him to reach free agency sooner. It has paid off in a big way, as Cespedes has been a +4.0 WAR player over the last year, hitting .277/.342/.504 in the process. For comparison, Cespedes’ deal with the A’s is basically Cody Ross‘ deal with the Diamondbacks, just with one extra year of team control. I’d call that a nice bargain.

Cespedes actually doesn’t lead the A’s in home runs over the last 365 days, though. That honor belongs to Brandon Moss, who has hit 31 bombs in his 489 plate appearances. The A’s signed Moss to a minor league contract at the end of 2011, after the Phillies outrighted him through waivers and every team decided to take a pass. Moss was called up on June 6th of last year and has mashed ever since, posting +3.2 WAR in the process.

We don’t have time to go through all of the rest of the hitters the A’s have cycled through, but it’s just more of the same idea. They spent $1 million on Jonny Gomes last year, then watched him mash as part of a DH platoon with minor league lifer Chris Carter. Carter was used as trade bait this winter to land Jed Lowrie, who has given them quality production while holding down both middle infield spots. At catcher, they’ve gotten quality production from George Kottaras (acquired after Milwaukee DFA’d him), John Jaso (stolen from the Mariners for a couple of lower level prospects), and Derek Norris (the third prospect in the Gio Gonzalez trade). They got Seth Smith from the Rockies for a couple of nothing pitchers and Josh Reddick from the Red Sox for Andrew Bailey.

Basically the A’s entire line-up came from somewhere else. Donaldson is the closest thing they have to a home grown player, but he was drafted by the Cubs and acquired only when he looked like a busted pick. This is an offense of veteran players that the A’s targeted as undervalued by the other 29 MLB teams, and that motley crue leads the majors in runs scored over the last year. While playing in a pitcher’s park.

You can run the same story on the pitching side. The A’s signed 39-year-old Bartolo Colon for $2 million, then re-signed him for $3 million this year, and he’s been one of the better starters in the American League in each of the last two seasons. Tom Milone was the throw-in fourth prospect in the Gio Gonzalez trade, and has been an above average starter since the day he got to Oakland. A.J. Griffin is a home grown player, but he was drafted in the 13th round of the 2010 draft, and he’s wildly outperforming all expectations for him as a prospect. Dan Straily was even more of a longshot, taken in the 24th round in 2009. The only premium arms they’ve relied on are Jarrod Parker (acquired from the Diamondbacks for Trevor Cahill) and Brett Anderson (acquired in the Dan Haren trade), and Anderson has been hurt for most of the last two years.

There’s not a Mark Mulder/Tim Hudson/Barry Zito trio of All-Star hurlers that every team covets here. There’s no Miguel Tejada or Jason Giambi. The 2012-2013 Oakland A’s are an almost complete embodiment of a team building a winner by targeting players who were undervalued by other clubs, beating everyone else with waiver wire pickups and secondary free agents who weren’t that highly regarded by the rest of Major League Baseball.

With a payroll of $50 to $60 million for each year, the A’s have built something of a juggernaut, almost entirely through bargain veteran acquisitions and looting other teams of their fringe prospects and role players. And they’ve run circles around the American League in the process.

This is probably Billy Beane’s best accomplishment. Getting this kind of production out of these players, in an era where nearly every team has an army of nerds looking for undervalued assets… it’s quite a story. And it’s one that probably deserves more attention than it has gotten.

Can they hang on to take the division from a very good Texas team once again? I don’t know. They’re fighting a bunch of really good teams, and they might not end up playing in October. There’s no “past calendar year” championship to celebrate, but that doesn’t mean we can’t recognize it anyway. 168 games playing .643 baseball with a shoestring payroll full of guys other teams didn’t see much value in. Kudos to the A’s front office. They know what they’re doing.