This is a pretty team-friendly deal for the ChiSox, who were supposedly shopping Danks earlier in the offseason. Danks was probably looking at $9 million in arbitration this year, so this is tantamount to buying out four free agent seasons at $14 million per year. Danks will be 31 when this deal expires, so if he pitches well, he's still in line to get a big payday.
The question for Chicago is, what Danks are they going to get? After a rough rookie season in 2007, Danks broke out in 2008, posting a 3.32 ERA and a 138 ERA+, along with a 3.44 FIP and a 5.2 fWAR. He seemed poised to establish himself as one of the top young pitchers in the league.
Since then, however, he's gone backwards...his ERA+ has dropped every season, and in 2011, he logged a 97 ERA+ and a 4.33 ERA (although his FIP was a more respectable 3.82). His fWAR hasn't come close to his 2008 5.2 mark since then, either, instead checking in at 2.9, 4.3, and 3.2.
Danks has been relatively healthy -- he was on the disabled list last season for the first time in his career, due to a strained oblique -- and is good for 200 innings per year. If you project him to continue as a 3 WAR pitcher during the life of this contract, then this is a reasonable signing...there's not going to be much surplus value, but Chicago should get their money's worth from him.
If you think, though, that Danks can take another step forward and be the 5 WAR pitcher he was in 2008, however, then this contract will end up looking like a steal.