Here in Week 7, it looms as a doozie in the revived NFC West.
They really shouldn't be. The foundation of Pete Carroll's physical defense has been under construction since he arrived in 2010. Seattle's back four make up the NFL's grittiest secondary. The front four uses speed and power to wreak havoc on quarterbacks. When playing as one, the Seahawks' defense can disrupt any team in the league.
Here's what they must do to beat the 49ers on Thursday night:
1. Contain Vernon Davis: The Seahawks don't get a break after contending with New England Patriots tight ends Rob Gronkowski and Aaron Hernandez on Sunday. Tight end Vernon Davis is equally dynamic in San Francisco's attack. If he finds a rhythm early with quarterback Alex Smith, he could throw Seattle off its axis. Davis frequently operates out of the slot, but he's a matchup nightmare from his natural tight end spot, too, and the Seahawks' front seven has their work cut out for them.
2. Rattle Alex Smith early: The 49ers are football's best team when they're ahead. Their offense is built to compile and nurse a lead. The New York Giants got to quarterback Alex Smith early and often last week. Coach Jim Harbaugh has coached Smith to avoid mistakes, emphasizing the need to throw the ball away in addition to avoiding sacks and bad decisions. But Smith stumbled into old habits once the Giants rattled him. That's problematic for Smith because the Seahawks -- anchored by ends Chris Clemons and Bruce Irvin -- might have the scariest pass rush in football.
3. Control the line: The 49ers' offensive line held the team back at times last season, but that's not the case in 2012. Led by the play of left tackle Joe Staley, San Francisco's offensive front has become the strength of this team. ProFootballFocus rates Staley as the game's best run blocker, but he's questionable for Thursday night with a concussion. The rest of the group has done a better-than-adequate job protecting Smith. Result: The 49ers look like something out of the 1920s when they're rolling. Carroll has confused opponents with multiple fronts in recent weeks. Overpowering San Francisco at the line of scrimmage could be the difference in what should be a sensational edition of "Thursday Night Football."
Follow Marc Sessler on Twitter @MarcSesslerNFL.