The Orioles need a first baseman. This is obvious. In 2010, the six players that donned a mitt combined for an amazingly low -1.1 fWAR. From Adam Dunn to Xavier Nady, there's a veritable alphabet soup that the Orioles could target to provide an easy three win (or more) upgrade over this year's club.
One option with which I am not enamored is Adam Dunn; certainly, I don't think the Orioles should offer 4-years and $15 million per season for him. There are a few reasons that I think Adam Dunn is a bad choice, some recounted ably by Dave Cameron:
1) He will cost the O's their second round draft pick.
2) There are lots of other, cheaper options for first base.
3) He's been worth $15 million or more exactly once in the past six seasons.
4) His "old player" skills and body type make me think he's susceptible to rapid decline.
5) His 2010 season showed a decline in walk rate and a rise in his strikeout rate, which combined for a very large increase in his K/BB ratio.
I think it goes without saying that Dunn's value lies entirely in his bat. At the very best, he's an average defender at first base (both Fangraphs and B-Ref have him as a -3 defender in 2010), and he's not going to provide any value on the bases (his last stolen base came in 2008). Historically, though, his bat has been a good one, driven by prodigious power and a keen batting eye.
From 2001 to 2009 he posted an aggregate line of .249/.383/.520 built on a .292 BABIP, 26.5% strikeout rate and 16.9% walk rate (1.57 K/BB ratio). His 2010 line, .260/.356/.536, doesn't look out of line at all with his career performance, but his ratios diverged significantly. His BABIP rose to .329, he struck out 30.7% of the time (previous high: 28.6% in 2004), and he walked in just 11.9% of his plate appearances (previous non-rookie half-season low: 15.8% in 2003). He had never before posted a K/BB ratio above 2.0. This season it spiked to 2.58. As Keith Law notes, he also saw the fewest pitches per plate appearance of his career in 2010. His batting eye clearly regressed in 2010; how much longer will the power last? Yes, Dunn has been durable and healthy, but that question makes me extremely hesitant to offer anything longer than a three year deal.
All told Dunn was worth about 30 batting runs last season, right in line with his average from the past six seasons. Subtract 10 for a positional adjustment, add 20 for replacement level, and assume 0 for his defensive abilities, and Dunn is a 4.0 win player. At $4m per win, that suggests he could get about $16m for a one year contract in 2011. I suspect that most teams, though, aren't going to value him as an average defender (knock off $4.0m), and a long-term deal may well come with a slight discount (knock off another $1m), right in line with the Fangraphs crowdsource (which has Dunn priced at 3/$12.5m) and Dave Cameron (who guesstimates 3/$11m).
I can accept that an offer of $15m per season may be what it takes to convince Dunn to come to the American League, but, for me, 4/$15m is just too rich a deal for a 31-year old bat-only player coming off a season where he showed some early signs of aging in the weaker league. This Orioles club isn't yet ready to contend, and if it is, it will be because the pitching takes a huge leap forward. If that happens, by all means, trade for someone like Adam Dunn. Right now, though, the money would be better spent targeting a cheaper option at first base and spending the balance on some more hitting prospects, including the one the O's could take in the 2nd round of a very deep 2011 draft class. First base shouldn't require an imperfect, expensive fix.