Smith is a cornerstone of that defense and has played a huge role in the success of Aldon Smith (no relation), who has an NFC-best 191/2 sacks. With Justin as the dominating physical presence, Aldon can loop around him, shoot into the backfield and get to the quarterback. Without Justin in the lineup, it's much easier for opponents to run at Aldon.
The other key defensive development is Seattle cornerback Richard Sherman's winning the appeal of his four-game suspension for violating the league's drug policy.
The Seahawks will get cornerback Brandon Browner back from suspension for the playoffs. He's the more physical of the two. Sherman is the playmaker, and figures to be a huge help for a team that's peaking at the ideal time.
Odds and ends
The 49ers are favored by 161/2 points to beat Arizona on Sunday in a game that will probably decide the NFC West champion.
If the 49ers win — or if Seattle loses to St. Louis — San Francisco will win its second consecutive division crown and play host to a playoff game.
According to odds expert R.J. Bell of Pregame.com, the 49ers have not been that big of a favorite since 1998, and the Cardinals have not been that much of an underdog since 1978.
Other observations by Bell on Week 17 games:
•Cincinnati is favored over Baltimore for the first time since 1998.
•Denver is favored by 16 over Kansas City, the biggest favorite the Broncos have ever been.
•In the last 27 times his team has been a home favorite, Washington's Mike Shanahan is 5-22 against the spread. That said, Shanahan has never lost against the spread when facing a Dallas Cowboys team coached by Jason Garrett.
•Pittsburgh Coach Mike Tomlin has never lost when taking the field with a losing record.
•Minnesota's Adrian Peterson needs to run for at least 208 yards against Green Bay to break Eric Dickerson's single-season rushing record of 2,105 yards. Las Vegas says there's an 18% chance of that happening.