KANSAS CITY, Mo. — Justin Houston cuts an imposing figure standing in front of his locker in the Chiefs' practice facility. The rookie linebacker is 6-foot-3, 270 pounds of muscle, his right eye a bloody red, a large scar on his chest and a tattoo inked across his right shoulder.

It's little wonder he's such a ferocious pass rusher that he recorded the first three sacks of his career last Sunday at Chicago. Who would want to get in his way?

Then you talk to him and you realize the image doesn't match reality.

Sure, he's a big guy with bulging biceps, but he's thoughtful and polite. The bloody eye came from getting poked a couple weeks back against New England. That scar across his chest is from when he had a cyst removed as a child. And the scrolling tattoo reads, "Only God Can Judge Me," a reflection both of his faith and his upbringing, which was never all that easy.

He's the sixth of 11 children raised by his mother, Kim Houston — nine boys and two girls in a crowded house in Statesboro, Georgia. His grandmother helped raise the kids, and although Houston said he knows his father, he was never a part of their lives.

"I don't know how she did it," Houston said of his mother, his sentences short and crisp, never revealing much beyond whatever is asked. "She's a tough woman."

Raised a tough son, too.

Backyard football games with his brothers were sometimes as competitive as what he's facing on Sundays, especially because there were so many siblings older than he was. Of course, little Justin never would back down, and that determination in part carried him to a football scholarship at Georgia.

"It does push you," he said, "because growing up, you see your older brother doing something, you try to do it like him. That's a big reason I'm here right now."

Houston stops midsentence as a couple of reporters with TV cameras approach, eager to talk about his masterful performance at Chicago. It was the culmination of a season's worth of work, of coming so close to a sack so many times and tackling nothing but air. Three times Houston brought down Caleb Hanie behind the line of scrimmage, the sacks a big reason why the Chiefs won 10-3.

Once the camera lights are turned off, and the lenses have moved off to some other corner of the locker room, Houston's voice drops as he talks about the trouble he ran into at Georgia.

Houston had just wrapped up a breakthrough junior season for the Bulldogs that included 10 sacks and his only interception. His draft stock had never been higher, especially given his ability to play in a 3-4 defense. It continued to rise when he went to the NFL Combine and produced 30 bench press reps, a 36.5-inch vertical jump, and a 40-yard dash that would make some running backs jealous.

Then word leaked that Houston tested positive for a banned substance — it was reportedly marijuana, though hasn't discussed it. He was immediately saddled with a reputation as a problem child, and when the draft began, he watched players with lesser resumes get selected, his first-round talent falling through the second round and into the third.

The Chiefs had already gambled on wide receiver Jonathan Baldwin in the first round, someone with his own baggage from college, but still thought enough of Houston to take a chance on him.

"This league is about the players, it really is," Todd Haley — who was fired as the Chiefs coach Monday — said. "You got to have good players. You see young guys come in that you feel like has lots of potential, but someone didn't take him first overall, so he was there when we had a chance to take him."

Like most rookies, the NFL lockout slowed Houston's development. So did protracted negotiations over his contract, which forced him to arrive late when training camp finally started.

Haley knew someone needed to emerge as a viable threat opposite Tamba Hali, the Chiefs' all-everything pass rusher. He started Houston in base defensive sets, and then tried him in sub-package work before he finally took over as an every-down player the past few weeks.

His numbers didn't reflect his performance against Pittsburgh, though he caused havoc for Ben Roethlisberger. The stat line finally showed up against the Bears, when he tore through a stout offensive line with a combination of speed and power that general manager Scott Pioli hoped to see when he called his name with the 70th overall pick in the draft.

"He's been doing a great job," said linebacker Derrick Johnson, who could set the franchise single-season tackles record in part because of what Houston and Hali have done on the edges.

Johnson and Hali were each drafted by the Chiefs, developed into stars and have signed long-term contracts to stay with the franchise. While it's far too early to say that's what the future holds for Houston, Haley makes it clear he has no ceiling. He may struggle in pass coverage, and he can get a little stronger and improve his technique, but all the tools are there to make that happen.

It's just a matter of making sure Houston continues to develop.

"The sooner that happens, the better," Haley said. "As we've seen the last couple weeks here, he's got a chance to be pretty good. You can't be starting off fast and let off. This will be a deal where we'll know a lot more as the season goes down the stretch, if he's going to continue to build on what he's put out there so far."