ATHENS, Ga. -- If the first half of the season proved anything about Georgia's defense, it's that the Bulldogs are versatile.
Defensive coordinator Todd Grantham has employed six different starting lineups in six games because of injuries, disciplinary issues and game situations.
But while the personnel was in a consistent state of flux, the defense's performance did not suffer. Georgia ranks among the nation's top defenses in every significant statistical category, confirming that the Bulldogs have caught on to the concepts in Grantham's 3-4 base scheme.
"I think just the way we installed and taught younger guys and collectively learned, it's just shown when people get injured or when things happen, we're not worried about the next guy coming in, because he's going to do well, because he knows what he's doing," said inside linebacker Christian Robinson, whose Bulldogs (4-2, 3-1 SEC) visit Vanderbilt (3-2, 1-2) this weekend.
The Bulldogs are third in the SEC in pass defense (174.7 yards per game), run defense (85.8 ypg), total defense (260.5 ypg) and scoring defense (19.2 points per game) and rank in the top 20 nationally in each category.
They posted those numbers despite having just five players -- Abry Jones, Jarvis Jones, Brandon Boykin, Sanders Commings and Shawn Williams -- who started all six games.
Starting inside linebacker Alec Ogletree broke his foot in the first quarter of the season-opening loss to Boise State, and Robinson suffered a foot injury of his own a week later against South Carolina, forcing true freshman Amarlo Herrera and junior Mike Gilliard into increased playing time.
Both players have performed well enough in the starters' absence that the Bulldogs will have a linebacker logjam when Ogletree returns for the Oct. 29 game against Florida.
Perhaps no player has made a more unexpected contribution than Gilliard. The junior from Valdosta, Ga., had 15 career tackles to his credit before this season but now leads the team with 40 stops -- a total that ranks 19th in the SEC.
Gilliard is this week's SEC Defensive Player of the Week after recording a career-high 12 tackles, a sack, 2.5 tackles for loss, a pass breakup, two quarterback hurries and a forced fumble in Saturday's 20-12 win against Tennessee.
"We have a lot of confidence in Michael now, as much as he's played and how well he's played," Georgia coach Mark Richt said.
Likewise, Williams, a starting safety, had to start at inside linebacker against Coastal Carolina in the first game after Robinson went down, but Herrera has since proved he can handle the playing time. He made six tackles in each of the last three games, all starts.
"I'm comfortable with what I do, and I really know for sure what I'm doing," Herrera said.
Just as the defensive staff found ways to use inside linebackers situationally once Robinson returned from his two-game absence, it rotated outside linebackers in Cornelius Washington's spot last week.
Washington, the team leader with 3.5 sacks, is serving a two-game suspension because of a DUI arrest, but Chase Vasser and freshman Ray Drew filled in capably for the pass-rush specialist at Tennessee. They combined for three tackles and two tackles for loss against the Volunteers, while the defense as a whole did not allow a touchdown until the game's final three minutes.
Georgia has won four consecutive games and has not allowed more than one offensive touchdown in any of those victories, even without top playmakers such as Ogletree and Washington in the lineup. Because of that ability to produce with a revolving door of available personnel, adaptability is quickly becoming a trademark of Georgia's defense.
"It's the mindset of the defense -- everybody taking it serious, knowing that any play you could be in the game, just paying attention and being mature about everything that goes on throughout the day," said Boykin, whose streak of 14 consecutive starts is seven more than Georgia's next closest defensive player. "I think the backups have done a good job of being on their keys and studying, so if they get in the game they know what to do. It's starting to show with Mike and all the other players when they get a chance to play."
Georgia hasn't finished a season in the nation's top 20 in total defense or scoring defense since 2007 -- the year Richt's club finished second in the final Associated Press poll -- but the Bulldogs' recent defensive dominance suggests that this might be the year the drought ends.
The 2007 team lost two early games before riding a second-half surge to a BCS bowl appearance. If these Bulldogs are to deliver a similar outcome, their defense will play a leading role -- particularly once Grantham gets all of his starters back on the field.
"They're gaining confidence," Richt said. "Coach Grantham's gaining confidence in them, and they're gaining confidence in what we're doing. I know I'm gaining confidence in them, and I'm enjoying a defense beginning to play like a Junkyard Dog bunch."
David Ching covers University of Georgia sports for DawgNation. He can be reached at firstname.lastname@example.org.