The Mariners are go with Michael Saunders over Dustin Ackley. There is going to be some rotation among the four outfielders - Saunders, Ackley, Raul Ibanez and Michael Morse over the next two months, trying to get them all at-bats. Obviously, if it gets to point where it's being completely detrimental in Ackley's conversion to outfield, they can send him back to Triple A Tacoma.
There is a hesitancy you see with Ackley in the outfield, which should be expected. He's so focused on making catches, that things like positioning, footwork and momentum when making throws kind of take a back seat. This process just doesn't happen over night. As has been mentioned before, when the Royals decided to convert Alex Gordon from third base to left field, while fixing his slumping bat, they sent him to Triple A for over 70 games. Because of Franklin Gutierrez being, well, Franklin Gutierrez, the Mariners haven't been able to make that commitment to Ackley learning the position.