The team has not yet confirmed the deal, which is pending a physical. The two sides were first reported to be engaged in "serious talks" by Ken Rosenthal of Fox Sports.
Oakland could use Butler as its DH. The Athletics received poor production from that spot in 2014, getting a .215/.294/.343 line from Alberto Callaspo, John Jaso and a bevy of other players. Butler had a down year for the Kansas City Royals, hitting .271/.323/.379, but the 2004 first-round draft pick enters the open market with a career .295/.359/.449 line, good for a 119 OPS+.
Butler became a free agent on Nov. 1 when Kansas City opted not to pick up his $12.5 million option for 2015, instead paying a $1 million buyout. The Florida native was recently predicted to receive a three-year, $30 million contract on the free-agent market by MLB Trade Rumors' Steve Adams.
Kansas City reportedly had a chance to match Oakland's offer but declined, per Jon Heyman of CBS Sports.
That might seem like a lot of money to give to a player who doesn't have any defensive value and is coming off of a season in which he was five percent below average at the plate, but Butler's home park might have been working against him, notes Royals Review's Kevin Ruprecht. That issue could work itself out in Oakland, despite O.co Coliseum being a noted pitcher's park, according to Fangraphs' Tony Blengino.