Before Oklahoma opened preseason practices last week, the nagging questions on offense mostly concerned the Sooners' suspension-ravaged receiving corps. Which turned out to be much ado about nothing much: With the reinstatement of veterans Jaz Reynolds and Trey Franks, the pending transfer of Penn State's Justin Brown and the long-awaited arrival of five-star freshman Trey Metoyer – not to mention junior Kenny Stills, whose status has never been in doubt – there will be as many viable targets for quarterback Landry Jones this fall as ever. But after an MRI confirmed a season-ending knee injury Monday for guard Tyler Evans, the fate of the suddenly depleted line charged with keeping Jones in one piece isn't going to be so easily resolved.

Evans' injury costs OU a seasoned senior with 29 starts at right guard over the last three years, less than a week after the abrupt retirement of another seasoned senior, center Ben Habern, who had accumulated 30 career starts. (Prior to the neck injury that ended his career, Habern's medical history included two season-ending ankle injuries in 2008 and 2009 and an arm injury that cost him nearly half of the 2011 campaign.) Even with regulars Lane Johnson (12 starts last year) and Gabe Ikard (25 starts over the last two years) still upright at left tackle and left guard, respectively, the line as a whole has gone from one of the most veteran fronts in college football – one of only eight nationally with at least 100 career starts among returning members – to one of the greenest before the opening kickoff.

"It's a couple of tough breaks but we've still got guys in there that we really like," Stoops said after Monday's practice. "I bragged about [junior guard] Bronson Irwin all winter and spring. I can tell he's in great shape here this summer. He must have did a great job. He'll have to really step up. But yeah, it makes you a little more thin."

If only youth was the most pressing issue. But there has also been a rapid depletion of available bodies to replace the starters. Will Latu, a 6-foot-5, 315-pound junior college transfer with designs on the right tackle job, failed to make the cut academically and signed with Arkansas State instead. (The Sooners' other top juco transfer, receiver Courtney Gardner, also fell short academically and will have to wait to join the team next year.) Incoming freshman John Michael McGee, once described as "a freak athletically" by offensive line coach James Patton, apparently quit the team Monday due to homesickness. (After coach Bob Stoops sent him home to mull his future, McGee wrote on his Twitter page, "Goodluck to OU on the field I'll be watching. It's just not for me.") Redshirt freshman Dylan Dismuke has been placed on medical hardship due to a lingering knee injury he suffered last December, effectively ending his career.

Two other backups, redshirt freshman Nila Kasitati and junior Austin Woods, were just cleared to practice on Monday despite Kasitati's recent surgery to repair a recurring heart condition and Woods' ongoing chemotherapy treatments against Hodgkins lymphoma. Including those two, the number of healthy, available linemen on the current roster stands at twelve – just enough to fill out a two-deep, as long as no one else gets hurt, gets in trouble or gets lost one too many times on the way to class for the rest of the year. At the very least, two or three true freshmen will be forced to burn their redshirts; at worst, one or two of them will be forced into a significant role.

That's not such an unusual story: Most teams will deal with a potentially crippling rash of injuries sooner or later, even if for the rest of them it will probably arrive later than the first week of practice. Not all teams operate within the razor-thin margin of error that accompanies conference and national championship hopes. The good news for Oklahoma is that the remodeled line now has a month to adjust to its new circumstances, followed by a pair of warm-up dates with UTEP and Florida A&M to open the season. Once they're into the weekly grind of the Big 12 schedule, though, the expectations here don't allow for much of a learning curve.