The San Francisco 49ers' veteran defense was the single NFC West unit I thought we could trust in Week 1.
Perhaps that will be the case in Week 2.
The 49ers have had many of the same defensive starters together for years, one reason they fielded the sixth-oldest starting defense in the league for Week 1. That defense didn't play its best in the opener. It played well enough last season for the 49ers to hold fourth-quarter road leads against the Minnesota Vikings and Indianapolis Colts. I would expected improved play over the coming weeks, despite some tough opponents.
Meanwhile, the Seahawks fielded the youngest starting defense in the division thanks in part to rookie free safety Earl Thomas.
Age by itself isn't necessarily an important indicator. But if a bad offense or defense is also an old one, we can often expect to see that unit dismantled the following offseason.
Note: Information is calculated using the rosters I maintain for every team in the league. Ages are calculated to the day, not to the most recent birthday (a player about to turn 30 would count as 29.9 instead of 29.0). Ages also reflect how old players were Friday, when I ran the calculations. This might seem like splitting hairs, but I point it out because the NFL produces more general averages.