IRVING, Texas - Jay Ratliff knows you had doubts.

How could you not?

He is the Dallas Cowboys' seventh-round pick from the 2005 draft, he hadn't played very much, and his time on the field was much like his personality away from it: invisible.

The first one he wanted to change, the second one he doesn't. But he never had a doubt he could do what he's doing now - even if maybe his own team did.

"I always knew I could do this," Ratliff said. "And if I couldn't do this, God wouldn't have put me in this situation. That's how I live life."

Of all the surprises this season, perhaps there is none greater than Ratliff. Pressed into the starting nose tackle spot because of a season-ending injury to Jason Ferguson in Week 1, the converted defensive end arguably has been Dallas' second-best defensive player.

He just really doesn't want to talk about it.

"I'm not seeking any glory, man," Ratliff said. "I'm not looking for any notoriety. I just want to do my job and go home."

But it's hard these days for him to remain a ghost. Despite being undersized for a nose tackle - he's listed at 6-foot-4, 298 pounds - he's second on the team with 12 quarterback pressures. He's one reason the Cowboys' run defense ranks fourth in the NFL.

"A lot of times in [the defense the Cowboys run] that guy has to be a stud and they have a heck of a player there," Detroit Lions coach Rod Marinelli said.

Who knew?

The Cowboys signed Tank Johnson, ostensibly because they thought he would be better than Ratliff or that Ratliff would wear out. What they didn't know was that the 26-year-old Ratliff has the motor of a 2-year-old, probably not that much different than that of his daughter, 2-year-old Christina. He never stops running.

"It's not in him to take a play off," defensive line coach Kacy Rodgers said.

So the Cowboys don't take him off the field often.

Despite Ratliff's productivity, fame eludes him. Some of it is the nature of the position. But mostly it's because of him.

"We were roommates at the D/FW Marriott my rookie year, and the guy didn't say two words to me," defensive end Chris Canty said.

When he does know you, the personality comes out. The loud laughter. The push-the-envelope sense of humor. It's at these moments you wouldn't necessarily guess both of Ratliff's parents are preachers.

"Jay is a person that once he trusts you, he trusts you," Canty said. "It's hard to earn that trust, but you love him and he can be the best friend you ever want to have or he could be the worst enemy you ever want to have."

There is the side within Ratliff that can pop, too.

Maybe the only place he truly is himself is at home, with his wife and their daughter. It's where he can listen to his daughter speaking French; his wife is a native of Martinique and French is her first language. It's where he can play "Halo," or the video game "Rock Band" with them.

There is more to Jay Ratliff off the field than he allows, and that probably won't change.

There is more to Jay Ratliff on the field, and that has changed . . . just as he thought it would.

"I've been through it before, so why should I be all worried?" Ratliff said.