Maybe the age is truly starting to get to Seau. Through the first 11 years of his career, he was one of the most healthy, dependable linebackers in the league. In the past four years, he has been plagued with injuries. Last year it was bad, this year it seems worse.
He is still playing great for us, and I hope he returns to us soon and doesn't miss any games... but I think after this season you will see him finally hanging up the towel (which is probably best)