The big news of the day, not just for A's fans but for baseball fans in general (due to the lack of other news), was the trade of Vin Mazzaro and Justin Marks to the Royals for David DeJesus.

DeJesus is a soon-to-be-31-year-old lefty outfielder who has played his entire career in Kansas City with little distinction. He finished sixth in the Rookie of the Year voting in 2004, as Oakland's own Bobby Crosby took home the award (that by all rights should have gone to Zack Greinke, who posted a 3.97 ERA in 145 innings). He led the league in hit-by-pitches in 2007 and was top-ten in triples from 2005-2009. Lack of distinction doesn't mean he's not a useful player, though -- his career on-base percentage ranks in the top fifty of active players and he is regarded as a fine defensive outfielder, capable of good work in center or excellent in a corner. At his peak (2005-2008), he was a two-and-a-half-win offensive contributor. Add that to whatever his glove is worth (half a win? A win? More?) and you get a guy absolutely worth the $2M to $3.6M he was making. He only played 91 games in 2010, however, as he went down in late July with a thumb injury that he never returned from. On the other hand, according to Corey Dawkins's DL tool, he's only been on the 15-day DL once in his career.

Bill James has DeJesus projected for a .340 wOBA next year (i.e. league average), but that's a higher mark than Ryan Sweeney, Coco Crisp, or Conor Jackson, and likely higher than whatever Travis Buck would project to if James had projected him. Only Chris Carter of potential A's outfielders beats DeJesus's projection, though park differences might have something to say about that: StatCorner has Kansas City with a 104 wOBA factor for lefties, compared to 95 in Oakland. That's a pretty significant swing, likely enough to drop DeJesus's projection down to basically the same range as Sweeney, Crisp, or Jackson (but definitely behind Carter, who was already projected into Oakland, where the RHB wOBA factor is even lower at 93).

So DeJesus is going to make $6 million to basically be the same as Ryan Sweeney or Coco Crisp or Conor Jackson. Why do the deal? First: injuries. Every person named in that sentence was hurt for significant periods of time in 2009. Assuming you don't have the money (or will) to sign Jayson Werth or Carl Crawford, or the trade chips to get whatever big bopper might be available, the next-best idea is to get extra average players so that when guys get hurt, you're not stuck playing Travis Buck, Matt Watson, Matt Carson, and Rajai Davis. Or putting Adam Rosales, Jack Cust, or Jeff Larish into the outfield. The jump from Jackson to DeJesus, in other words, is minimal (though the defensive bump is nice). But if DeJesus or Crisp or Carter (my presumed starting outfield) goes down, the drop-off to Conor Jackson is a very different thing than the drop-off to Rajai Davis (who should be reduced to caddying for Chris Carter and pinch-running for all and sundry).

Second reason you do the deal: Vin Mazzaro's value is at its highest point right now. He's a supposed ground-ball pitcher who doesn't get ground balls. He doesn't miss bats. His control is solid, but his walk rate isn't low enough to make his K/BB stellar. He doesn't do Dallas Braden-like things with the glove or holding runners. And on top of all this, he might, as Ken Arneson posited earlier today on Twitter, be a dummy or a head-case -- see the weird demotion to Sacramento late in 2010.

Mazzaro is likely not better than a million other guys who could step in if the A's front-line starters go down, guys like Tyson Ross or Clayton Mortensen. The question, then, is "who is Justin Marks"? And here's what I'll tell you: I dunno. Baseball America had him 27th in the A's system coming in to 2010. He was a third-rounder out of Louisville in 2009. BA called him "polished" but said that he had no plus pitches, and tapped his upside as back-of-the-rotation starter with the chance to reach that potential fairly quickly. John Sickels game him a C+, a fine grade for a guy who hadn't even recorded a professional out (he got into one game in rookie ball, giving up three hits and four walks without retiring a batter). His writeup agreed with BA's, describing him as a strike-thrower with better velocity than most finesse guys, but not enough to call him a power-pitcher.

In other words, if things go right for Marks, he can grow up to be ... Vin Mazzaro. A guy who won't kill you if you're using him as a 3rd or 4th starter, but who isn't really pushing you to a championship either. These guys are bellwethers, basically. If they're your 3rd starter, then say hello to 72 wins. Fourth, you should be right around .500. Fifth, and you've probably got yourself a very good rotation that can get you into the playoffs. If you trust your player development team, these are guys you can trade because you can draft three to five new copies of them every year in perpetuity.

I'm not going into a winners or losers discussion here. I'm not JC Bradbury, but I also find most argument of that sort tedious, especially given the multitude of factors unrelated to pure bat-and-ball, like contract status, compensatory draft picks, differing locations in the competitive cycle, and so forth. There's also information we're not privy to -- medical reports on everyone involved (including everyone peripherally involved, like the other A's outfielders) , an understanding of Mazzaro's mental and emotional state, scouting reports on Marks, and future plans (no trade or signing is one-off -- there is always a larger agenda into which a given transaction fits).

All that said, I am pleased with the trade, even just from a pure fan's perspective -- I've long admired DeJesus's game and I'd grown rather tired of Vin Mazzaro's ball-in-play stylings, so, seeing as how the minor leaguer involved isn't a stud waiting to happen, I'm feeling positive.

One last note: Baseball-Reference's implementation of Bill James's similarity scores lists DeJesus's third-most-similar batter (and second-most-similar through age 30) as Coco Crisp. (His 9th-best comp, by the way, is good ol' Pistol Pete Reiser, the great Dodgers outfielder of the '40s who led the league in OPS in 1941, went to war from '43 to '45, and was washed up at 29, mainly because he couldn't stop crashing into walls. Ring Lardner, if I remember correctly, wrote a great profile, and this Steven Goldman piece at Baseball Prospectus is also recommended.)