The Mariners announced on their Twitter feed that they have sent shortstop Jack Wilson to the Atlanta Braves in exchange for a player to be named later. Wilson is on the disabled list at the moment but is eligible to come off of it this week.
Atlanta is clearly seeking some middle infield depth here, as Wilson is one of the better defensive middle infielders in the game and has held a job in the majors for a decade now because of it. He's struggled a great deal with the bat of late, posting an extremely weak 61 wRC+ over the past two seasons, but at the very least Atlanta shouldn't expect to lose much on defense when Alex Gonzalez isn't manning the position.
As for Seattle, Wilson hasn't been in their plans for a while now. Dustin Ackley is the real deal at second base these days and Brendan Ryan is getting most of the playing time at shortstop, so it's not surprising to see the Mariners free up the roster spot for someone that's younger. Seattle's current roster features intriguing young position players like Ackley, Kyle Seager, Mike Carp, Trayvon Robinson and Casper Wells, so presumably they'll try to work them into the lineup as much as possible over the season's final month.