The Bengals played without Leon Hall for nearly half of last season, and it didn’t matter, even though the injury came only a few months after Johnathan Joseph departed for Houston. Nate Clements was signed to fill the hole left by Joseph, and the other hole left by Hall was partly filled by Pacman Jones, but mostly by another group of players who had no role whatsoever in the defensive backfield.

Even when a secondary is depleted, defending the pass becomes much easier when opposing quarterbacks are busy staring upward at a pleasant blue sky instead of scanning for targets downfield. The Bengals allowed 211.6 passing yards per game last year, a result powered largely by their pass rush and its 45 sacks. That pressure can and should continue this year, but a defense can’t sustain itself on that alone, especially with Clements aging and his coverage skills rapidly declining.

That’s why the Bengals used one of their two first-round picks (17th overall) on Alabama cornerback Dre Kirkpatrick this past April. With the swift uptick in passing and Dan Marino’s single-season passing yards record broken twice last year after it stood for 26 seasons, the league-wide emphasis has fallen squarely on passing, and defending the pass.

But now with Hall still recovering from his torn Achillies, there’s a chance the Bengals could be playing without Kirkpatrick in early September.

In this morning’s links post we passed along the initial reports regarding Kirkpatrick’s knee injury, and it was widely assumed that he’d be sidelined for about a month. That’s now been pushed back by two weeks, according to reports from NFL Network, a vast difference for a rookie who will be tasked with shutting down Pro Bowl wide receivers and quarterbacks.

Specifically, the injury is a fractured knee suffered while Kirkpatrick was preparing for training camp. If there isn’t a setback and he maintains the projected six-week timetable, he’ll be able to resume football activities about one week before the 2012 NFL season kicks off.

That’s one week for a rookie to re-start a normal conditioning routine, be re-introduced into defensive schemes, and gameplan for his first professional game that matters, all after missing his first professional training camp that matters. It’s not going to happen, meaning there’s a very real possibility the Bengals will be playing without a player they invested highly in for two important early games against dangerous passing offenses.

It’ll start right away with the division rival Ravens. Joe Flacco may be inconsistent, but if he’s staring at a backfield with Clements and some grisly combination of Pacman Jones, Terrence Newman, or Jason Allen as starting corners, eyes will widen as Torrey Smith and Anquan Boldin trot freely downfield. In Week 11 last year Smith caught six passes for a season high 165 yards against Cincy.

The Bengals will surely be cautious with their first-round pick and give him the abbreviated Prince Amukamara treatment. Amukamara fractured a bone in his foot at the beginning of training camp last August. The Giants first-round pick in 2011 was then placed on the physically unable to perform list, and he didn’t appear in a game until Week 11.

Kirkpatrick’s injury doesn’t sound nearly as serious, and it won’t require an absence that’s nearly as long. But there’s still a strong possibility that he’ll be out for that season opener against the Ravens, and he’ll likely still be out two weeks later when the Bengals face Bob Griffin in his third NFL game.