ATHENS — One year from now, Jeff Owens could be competing for a starting job in the NFL.

In the meantime, Owens says it's a challenge just to keep his starting job for No. 1 Georgia.

Owens is considered a possible first-round pick in the 2009 NFL draft, but the Georgia senior defensive tackle can't relax. He says he could be a backup any week on Georgia's deep defense.

If Owens is worried, that's OK with Georgia defensive coordinator Willie Martinez. Even established starters like Owens, who started 13 games last year, have no guarantees for extensive playing time as Martinez uses a liberal substitution pattern to keep his players fresh.

The depth of talent throughout the defense, which returns nine starters, is a big reason Georgia topped the AP preseason poll.

"I thought the biggest key to our team last year was playing a lot of guys, probably more guys than in any year I've been at Georgia," said coach Mark Richt. "It was not because we had to or needed to because of injury, but because we thought they deserved to play.

"We have a lot of guys coming back who have played a good bit, and hopefully we can continue that trend."

Georgia finished 14th in the nation in total defense and led the Southeastern Conference in sacks last season.

Owens and Geno Atkins, a junior who had 7.5 sacks last season, are the starting defensive tackles. But Martinez says there's no drop-off with backups Corvey Irvin and Kade Weston, who made five starts last season.

"We push each other to be better," Atkins said. "We're competing on the field to try to make a play. It's a good competition."

The depth at defensive tackle keeps coming in waves, with sophomores Brandon Wood and Ricardo Crawford and freshmen A.J. Harmon and DeAngelo Tyson.

"The rotation keeps us fresh, but the more competition is more of a challenge," Owens said. "We've got guys pushing us. Each week we could lose our starting job. I could be starting and the next week Corvey could be starting. That's why we compete in practice to earn our spot. We are fighting for a starting job because nothing is set in stone."

The depth leads to intense practices. It also keeps the Bulldogs hustling in games.

"You can't take a play off," Owens said. "It's easy to take 95 snaps and take off 40 of them. But if you take 40, you have to play all 40 full-speed."

Atkins was a first-team all-SEC pick last year despite starting only seven of 13 games. Georgia had 23 players with 10 or more tackles and 29 who played in at least 10 games.

Martinez said depth on defense is more important as he tries to keep up with modern offenses.

"You face all these spread offenses and they're stretching the field and putting pressure on defenses to run to the football," Martinez said. "I don't know if anybody can play 60 snaps right now at full speed, and I don't know if that's what you want. You'd rather have a guy who's fresh."

Martinez said he doesn't want backups on the field who can't play like starters.

"You want guys who know what to do and you want playmakers," Martinez said. "You want productive players. We're not going to substitute just to substitute. When we substitute, we feel like that guy deserves reps because he's earned it."

The depth has taken some hits at some positions.

Backup defensive end Michael Lemon was dismissed from the team last month following an arrest for misdemeanor battery and felony aggravated battery. Georgia also is dealing with injuries at defensive end.

Safety Donavon Baldwin, a third-team player on the preseason depth chart, was suspended indefinitely for off-field problems. Linebacker Darius Dewberry, a top backup, was suspended for the first two games.

Even so, Martinez expects to rotate as many players in the Bulldogs' Aug. 30 opener against Georgia Southern as he used in rotations late last season.

"We like the competition," Martinez said.

"If you're not going hard on every play, we're going to take you out."