Beltre, or Scott Boras rather, seems to still be pressing for a multi-year contract for Beltre, something in the 4/40 range. It strikes me as unlikely that Beltre will reach that. He may get $10 million in annual, but guaranteed for four years coming off the season he had in 2009, the reputation that he's garnered and the general state of free agent contracts this winter, seems unlikely. Beltre and Boras are probably aware of that. They probably know that they are more likely to prefer a one year contract in order to have Beltre put up respectable offensive numbers and then land a four year deal next winter. By declining arbitration, they are refusing a guaranteed one year, ~$12 million contract.
What this tells me is that, while the Mariners are objectively no different from any of the other 29 teams in terms of chance of signing Beltre, realistically, they don't want him to return for 2010. I do not blame them.
In his five years here, Beltre provided legitimately top of the line defense (48.2 runs by UZR), a dedication to play through all sorts of pain as long as it didn't impact his ability to play, fantastically easy to root for antics and many other things. According to FanGraphs, Beltre was worth 16.6 wins with the Mariners, an amount that from 2005-9 was valued at $67.4 million for which he was paid $64 million.
Everything that Adrian Beltre did not provide is irrelevant. He was worth his salary in performance on the field alone. His performances in other aspects, the dancing, the lovable plate discipline, the interactions with Red, etc were just gravy. Godspeed, Adrian. I hope you find success and appreciation where ever you go*
*offer void in Anaheim