Calling anyone the worst at anything can be pretty harsh, and such terms are bandied about too lightly. Being the worst is, at the very least, different than being the least valuable, or biggest negative if you will. For example, the worst player in baseball this year was probably the Royals' Tony Pena, who was both a poor shortstop and a poor hitter - he reached base in 7 of 53 plate appearances. However there is a limit to what even teams like the Royals can take, and even they, mercifully, got rid of him.
So Tony Pena may have been the worst player in the majors this year, but he did not hurt his team the most, simply because players that bad rarely stick around in the majors. No, to really be the worst overall, or the least valuable you have to be good enough or fortuitous enough to play pretty much the entire season, so your lousiness can have the most impact. Generally there are three types of players who fit this bill - young, theoretically promising players, great defenders or players at important positions (see MacDonald, John), or players whose terribleness is not widely known. This year the worst hitters that qualify for the batting title mostly fit these bills. (Note: I used OPS as a cut and dry counting method, but stats like wOBA and GPA produce essentially the same lists of players and orders)
Worst Hitters in Baseball
Hitter OPS Other
Willy Taveras .555 (Fast, centre fielder)
Jason Kendall .598 (Catcher)
Emilio Bonifacio .611 (Young)
Edgar Renteria .625 (Shortstop)
Kazuo Matsui .645
Chris Young .655 (Young, centre fielder, demoted)
David Eckstein .663
BJ Upton .666 (Young, centre fielder)
JJ Hardy .667 (Youngish, shortstop, demoted)
Randy Winn .677
Jeff Francoeur .682 (Youngish)
Daniel Murphy .683 (Young)
Adrian Beltre .686 (Good defender)
Russell Martin .692 (Youngish, catcher)
Rafael Furcal .692 (Shortstop)
Ryan Sweeney .695 (Young, centre fielder)
Elvis Andrus .698 (Young, Shortstop)
Orlando Cabrera .702 (Shortstop)
David Ortiz .704
Andy Laroche .705 (Youngish)
Vernon Wells .706 (Centre fielder)
Bengie Molina .709 (Catcher)
Jimmy Rollins .709 (Shortstop)
On the hitting side of the equation then, Vernon Wells is one of the least valuable players, although he isn't that close to being the worst hitter in the bigs. An interesting note is that pretty much all of these players play in the National League... Anyway, as you can see, with the exception of a few washed up veterans (David Eckstein, Kaz Matsui, Randy Winn), pretty much all the worst hitting players in baseball are young or play short, catcher or centre field - ie there is a reason why they are still in the majors despite their poor hitting: their defense or their potential. However not all of these players are good defenders, nor do all of them have potential. We'll take a look at the worst fielders in baseball this year. (We're using UZR here, prorated to 150 games, because it's one of the more available and reasonably reliable stats out there. Catchers are not included.)
Worst Fielders in Baseball (now including Adam Dunn!)
Fielder UZR 150
Adam Dunn approx. -32.9 (1B, RF, LF combined)
Vernon Wells -24.4
Chipper Jones -20.7
Yuniesky Betancourt -18.8
Dexter Fowler -18.3
Andre Ethier -18.1
Brad Hawpe -17.2
Jermaine Dye -17.1
Mike Lowell -16.1
Jason Bay -14.5
Carlos Lee -14.5
Michael Young -13.8
Jacoby Ellsbury -13.2
Skip Schumaker -12.8
Johnny Damon -12.2
Orlando Cabrera -12.2
Alberto Callaspo -11.3
Michael Cuddyer -10.9
Shane Victorino -10.1
David Wright -9.8
Alex Rodriguez -9.7
So if you were paying close attention, you'll notice that only two of these names overlap - Orlando Cabrera and Vernon Wells. Wells has been a spectacularly, historically bad fielder this year, easily the (second) worst in baseball. This isn't a fluke either, he was exactly as bad last year. Orlando Cabrera's in a similar boat, though he isn't as bad a fielder and he's also a shortstop. Does this make them the two worst players in baseball? Well, no. There are a lot of guys who are both bad hitters and bad fielders who maybe show up on one list but not the other - Emilio Bonifacio comes to mind, and David Ortiz doesn't really defend enough to qualify. Some of these defenders also don't qualify for the batting title, my fairly arbitrary cutoff for hitters, like Yuniesky Betancourt. If we take a look at a measure that combines both offense and defense though, we get a better picture of overall lack of value. (We're using runs above replacement here, which includes offense and defense, position and league adjusted, with no minimum at bat threshold.)
Least Valuable Players in Baseball
Player Runs Above Replacement
Jose Guillen -17.8
Brian Giles -17.0
Yuni Betancourt -15.8
Alexi Casilla -13.8
Delmon Young -13.8
Gary Matthews Jr.-12.5
Conor Jackson -10.5
Eric Bruntlett -10.4
Aaron Miles -10.4
Mike Aviles -9.8
Vernon Wells -9.6
Matt Tolbert -9.2
Emmanuel Burris -8.6
Garret Atkins -8.3
Chris Davis -8.2
Reggie Willits -8.0
Josh Fields -8.0
David Ortiz -7.8
As you can see, most of the names here don't appear on either of our lists above, because pretty much every player on the list has been demoted, injured or consigned to part time duty. In fact, the only regulars on that list are Yuniesky Betancourt, Vernon Wells and David Ortiz (well, and sort of Garrett Atkins.) In our quest to find the least valuable player in baseball then we have three finalists and one clear winner... Yuniesky Betancourt. (What, you thought I was going to say Vernon?) Betancourt really has been the best of the worst, at least amongst those currently employed. He's a terrible fielder and an even worse hitter. After that though it's a bit of a toss-up between Vernon and Papi, as they've both hit about the same, and deciding whether not fielding or being a terrible fielder is worse is mostly academic. Still, even if you quibble with particular stats, methodologies and data, its hard to argue with what is a pretty broadly painted picture of Vernon Wells' value
So there you have it folks: Vernon Wells, (second) least valuable every day player in the majors. And hey, he's only being paid a bajillion (or 85 or whatever) million dollars more.
All stats courteous the ever fantastic Fangraphs.