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Washington Nationals' Josh Willingham (16) is congratulated at home by Ryan Zimmerman (11) and Cristian Guzman after hitting a grand slam during the fifth inning of a baseball game against the Milwaukee Brewers Monday, July 27, 2009, in Milwaukee. (AP Photo/Morry Gash)

The A's have acquired outfielder Josh Willingham from the Washington Nationals in exchange for two players, a major league source confirmed to Bay Area News Group on Thursday morning.

The two players the A's are dealing aren't known. At least one has major league experience, the source confirmed, though it isn't believed either was a key member of the A's 25-man roster last season. The deal has been agreed upon, with only final details to be ironed out. An announcement could come Thursday afternoon.

Willingham, who turns 32 in February, hit .268 last season with 16 homers and 56 RBIs. He hit 15 of those homers before the All-Star break, but then underwent left knee surgery in August that ended his season. He's hit 20-plus homers three times in his seven-year major league career, most recently in 2009 when he had 24.

He made $4.6 million last season and is eligible for arbitration one last time this winter before becoming a free agent after the upcoming season.

Willingham played strictly left field last season, and it's logical to assume he'll take over left with the A's, with Coco Crisp in center and David DeJesus in right. DeJesus was acquired from Kansas City in November, and he's pegged for a starting role.

If Willingham starts, it would push Ryan Sweeney to the bench. Sweeney is one of Oakland's better all-around players, but he's hit just 12 homers in his three seasons with the team. A lack of power among the A's outfielders has been an offensive weakness.

Sweeney is coming off knee surgery of his own that ended his 2010 season early, but he's been optimistic he'll be ready by spring training.