Rhodes, 54, entered a hospital Sunday for tests. Doctors still don't know the cause of his symptoms, so the NFL veteran will take this week to rest and to undergo further evaluation.
Rhodes, took over Seattle's defense prior to the 2003 season. Linebackers coach John Marshall will fill in as defensive coordinator during Rhodes' absence.
Before joining Seattle, Rhodes ran the defense in Denver for two years. He also spent a season as the defensive coordinator for the Washington Redskins, a year as head coach of the Green Bay Packers and four years as the Philadelphia Eagles' head coach.
In the early 1990s, Rhodes was the Packers' defensive coordinator under Mike Holmgren, who later hired him in Seattle.