Linebacker Malcolm Smith has played for Pete Carroll long enough, first at USC and then with the Seattle Seahawks, that he knows nearly all the intricacies of their defensive system.

It's a good thing he has that background. It's one of the biggest reasons that despite being a seventh-round pick he's been able to find a spot on the Seahawks roster.

Smith's versatility is being put to test again. For the second time this season, Smith is being called upon to fill in for an absent starter. Earlier, he was Seattle's starter at strongside linebacker when Bruce Irvin was serving a four-game suspension. Now he's being asked to start at weakside linebacker with K.J. Wright out at least a month with a fracture in his right foot.

Meanwhile the Seahawks placed backup strong safety Jeron Johnson on injured reserve and re-signed cornerback Perrish Cox on Wednesday.

Johnson sustained a significant hamstring injury Sunday in Seattle's loss at San Francisco. In order to have enough depth in the secondary, Johnson was placed on injured reserve and Cox was re-signed.

Cox was signed by Seattle on Nov. 26 but was released a day later. Cox said being released after a day was due to the Seahawks uncertainty about the status of cornerback Brandon Browner.

Seattle coach Pete Carroll said the plan in the secondary is to have DeShawn Shead work exclusively at safety and have Cox play cornerback. Shead had been working at both positions as a backup