Smith, 31, batted .253/.329/.391 with eight home runs in 410 plate appearances for Oakland this season. Always a better hitter against right-handed pitching, he continued that trend in 2013, posting a .748 OPS against right-handers and just a .621 mark against lefties. For his career, Smith has mashed right-handers to the tune of a .279/.357/.487 batting line. Smith's defense in left field has consistently graded out as a positive (+7.7 UZR/150, +2 Defensive Runs Saved), but he's limited to a corner position and hasn't received great marks in right field.
MLBTR contributor Matt Swartz projected Smith to earn $4.3MM this offseason in his final round of arbitration. He's eligible for free agency next winter.
Gregerson, 29, is also a free agent following this season and projected to earn a comparable $4.9MM salary, per Swartz. He enjoyed yet another strong season in the Padres' bullpen last year, pitching to a 2.71 ERA with 8.7 K/9, 2.4 BB/9 and a 45.5 percent ground-ball rate. Gregerson is the second high-profile reliever added by the A's in the past 24 hours, as GM Billy Beane also acquired Jim Johnson from the Orioles last night.
The trade was first reported by Oakland-area blogger Chris Kusiolek (on Twitter).