In biology you learn about keystone species. A keystone specie is a specie that has a disproportionate effect on its environment relative to its abundance. Example: the Puget Sound starfish is the only predator for the area’s sea urchins. Remove the starfish, and the sea urchin population explodes before utterly overwhelming the creatures/organisms that it preys on. In other words, domino effect.

Insert Osi Umenyiora. Or, rather, exit Osi Umenyiora. The sixth-year defensive end tore the lateral meniscus in his left knee Saturday, ending his season and destroying the environment for what now appears to be an 8-8 team. The New York Giants lost more than just 12-15 sacks when Umenyiora went down.

The ascension of Justin Tuck came to a screeching halt. Dominant as the third best pass-rusher on the club last season, Tuck now becomes the primary focus of every opposing offensive line. This for a guy whose engine tends to sputter ever so slightly against double teams.

Forget the idea of New York’s defensive tackles elevating their game in ’08. If offensive lines aren’t sliding protection to Umenyiora on the outside, Fred Robbins isn’t attacking interior linemen from an advantageous angle. Same goes for Barry Cofield.

Thus, the Giants will have to call on more blitzes from their linebackers. Making matters difficult for the linebackers is the fact that pass-rusher Mathias Kiwanuka will now likely have his hand in the dirt, meaning New York will ask solid but never spectacular Danny Clark to be a playmaker. Clark is a two-down player. Which leads to the afterthought of, What happens to the run defense now that Umenyiora’s backside speed is gone?

Maybe opponents won’t run against the Giants anyway. After all, with a tepid pass-rush, quarterbacks will start to see corners Cory Webster and Aaron Ross in a different light. With all day to throw, that light will often be green. And first-round rookie Kenny Phillips, who has looked sharp thus far, will begin to dull once the duration of his coverage responsibilities extends by two or three seconds each play.

Is the situation really this bleak for the defending Super Bowl champion Giants? Yes. Without a pass-rush, New York’s defense is average at best.

Searching for a flicker of hope, we come to the part of the column where the name Michael Strahan appears. For $8 million, the Giants can re-introduce the future Hall of Famer back into their environment. They’d have to treat the soon-to-be 37-year-old time like an endangered specie, giving him time off during the week and limited snaps in September. But last year showed that this does not create a problem. Of course, it doesn’t completely fix one either.