Cornerback Lardarius Webb, signed to a six-year, $52 million deal this offseason, went down in a heap and immediately grabbed for his knee following a coverage play in the first half. Webb was sent to the locker room after not being able to put any weight on the leg as he left the field.
According to Aaron Wilson of the Baltimore Sun, team sources believe that Webb tore his anterior cruciate ligament (ACL). Ravens head coach John Harbaugh was also fearful of that diagnosis in his postgame press conference.
Webb will have an MRI on Monday to confirm the injury.
If Webb does have a torn ACL, he'll likely miss the rest of the 2012 season. New York Jets cornerback Darrelle Revis suffered the same injury three weeks ago and was placed on season-ending injured reserve.
The Ravens would be losing their top overall cornerback from a defense that is already reeling.
According to Pro Football Focus, Webb had allowed just 10 catches for 93 yards and zero touchdowns through five games in 2012. His catch rate allowed (43.5 percent) and passer rating against (37.0) both ranked near the top of the NFL among cornerbacks.
The shutdown corner would be replaced by a combination of Jimmy Smith, Cary Williams, Corey Graham and Chykie Brown.
Cowboys quarterback Tony Romo attacked the backups once Webb went out, including a late touchdown to Dez Bryant and a defensive pass interference call on Brown that set up the Cowboys for a final field-goal attempt.
The Ravens were lucky to get a dropped two-point conversion and missed field goal that helped Baltimore escape with the win.
To put Webb's impact in perspective, consider how both Smith and Williams have played in featured roles so far this season.
Williams, a starter opposite Webb, has allowed 26 catches for 387 yards and a touchdown in 2012. Smith has given up 10 catches for 153 yards over just 209 snaps. The two have combined for five penalties.
The Ravens, who were gashed again on defense this week, will need both players to step up their respective games with Webb likely out.
One other important effect of Webb's injury: Baltimore will also need to replace him as the slot cornerback in the nickel. Webb played 91 of his 378 snaps there, and PFF graded him out as the best cover corner in the slot in 2012 through five games.
On nine slot targets, Webb allowed just three catches for 27 yards for a passer rating of 3.7. He also intercepted a pass from the slot.
Graham, mostly a special teams player in his NFL career, will likely take over most of the nickel cornerback snaps. Smith is expected to play outside.
While Ray Lewis and Ed Reed receive the most publicity on the Ravens defense, Webb was one of the players Baltimore could not afford to lose this season. If he is in fact gone for the rest of the year, the Ravens' chances of playing into February take a big hit.