The Rays traded Lopez and Jeffrey Springs to the Athletics on Saturday in exchange for Joe Boyle, Jacob Watters, Will Simpson and a compensatory draft pick.
Lopez appeared in four games for the Rays last season, giving up six earned runs while striking out eight batters and walking seven across 10.1 innings. His performance improved slightly in Triple-A (4.26 ERA, 1.32 WHIP over 88.2 innings), and his chances of making the Athletics' Opening Day bullpen will likely depend on how well he does during spring training.