Today: he’s up, called up from Tacoma.
Ackley was hitting .300 and getting on base at a .418 clip through 326 plate appearances, and adding some power (.487 SLG) to boot. His not being promoted before now was almost certainly a function of Super Two calculation, but you’ll have that. He should likely be plugged right in the Mariners’ lineup, giving it a bit of OBP and doubles power that it sorely lacks at the moment.
This likely means that some combination of Adam Kennedy, Jack Wilson and Chone Figgins will either be gone soon or will see reduced playing time. But it’s not like that’s a bad thing.