"This was a team that was very aggressive in coming after Josh," Seattle general manager John Schneider said. "They were in a situation where they have a strong need. It has more to do with how Walter has stepped up and how [Marcus Trufant] is playing and some of the younger guys."
The move came just as the Seahawks were wrapping up practice on Tuesday, a practice that Wilson participated in before receiving word of the trade.
Wilson spent his first three seasons with the Seahawks after being a second-round pick out of Maryland in 2007. Wilson started 23 of 28 games the last two seasons and took both of his interceptions a year ago back for touchdowns.
Wilson also has been a standout on special teams, averaging 27 and 25 yards per kickoff return his first two years in the league.
Also playing a role in the deal was Wilson's status as an unrestricted free agent after this season. In Baltimore, he'll fill a need created when cornerback Domonique Foxworth tore up his knee during a pre-camp drill.
"With Josh in terms of the value it was at a level with him being an unrestricted free agent after the season, it was at a point where we felt was definitely fair," Schneider said.
With Wilson gone, Carroll said Jennings will step into the starters role opposite Trufant. Jennings, nicknamed "Slim" because of his slender 180-pound frame, has started 29 of 64 games since being a first-round pick in 2006. But his lack of weight has led to Jennings getting isolated against bigger receivers in the past. He has just one interception in four season.
Thurmond will step into the fifth defensive back spot, less than a year after a devastating knee injury that cost him most of his senior season at Oregon. He'll share some of his nickel duties with safety Jordan Babineaux and Roy Lewis. Running back Leon Washington will become the Seahawks primary kick returner.
"Walter has had a great camp. He's played beautifully," Carroll said. "He's played almost more than anybody else so we've gotten a great look at him and really excited about his contribution."