PITTSFORD, New York -- Giggling uncontrollably, Marcell Dareus was still having a difficult time containing his excitement Sunday, a day after getting a first glimpse of the Buffalo Bills' revamped, high-priced defensive line's potential.

There's no question, Mario Williams and Co. looked impressive in their first practice in shoulder pads Saturday, three days into camp.

"Shut your mouth," Dareus, the second-year defensive tackle from Alabama said, before bursting into a fit of laughter. "There's really not much I can say except, what you see is what you get. I don't think we're overrated. I don't think we're underrated. I think we're right where we're supposed to be."

And that could well spell trouble for opposing offenses after the Bills spent considerable time and money upgrading what had been a porous line that also had difficulty generating a pass rush.

None of the problems of the past were evident in a practice that left coach Chan Gailey calling his defense's performance "dominating."

No surprise, Williams -- the Bills' newly signed $100-million defensive end -- was in the thick of creating much of the havoc.

He and tackle Kyle Williams disrupted a running play so quickly that Fred Jackson barely got the handoff when Mario Williams stopped him in his tracks by grabbing him by the shoulder pad.

Jackson was so surprised that he went up to quarterback Ryan Fitzpatrick and joked: "I think Mario could've taken the handoff before I did."

And that was just one of numerous highlights.

A few plays later, Mario Williams wasn't fooled by a misdirection play, staying to his left and forcing Fitzpatrick to throw the ball away.

Then Williams and Dareus teamed up by bursting into the backfield to get what would've been a sure sack.

Kyle Williams was cautiously impressed, noting this was only one practice.

"We're still building, but you know it's always nice to have good days," he said. "We've talked about what it looks like by just looking at the names written down. Sure that looks good. But can we take it and put it on the field? And that's what we're trying to do now."

The list of names are easily recognizable on a starting line made up of the two Williams, Dareus and Mark Anderson, another free-agent addition and former Alabama standout, who's penciled in on the right side.

And then there's a solid group of established veterans filling backup positions such as defensive ends Shawne Merriman, Chris Kelsay and Spencer Johnson, and tackle Dwan Edwards.

Kelsay considers both the line and defense as a whole as the most talented and depth-laden the Bills have had since he arrived in 2003.

And that's saying something considering the Bills finished ranked second in the NFL both 2003 and 2004 with a defense that included tackles Pat Williams and Sam Adams, pass-rusher Aaron Schobel, linebackers Takeo Spikes from Auburn and London Fletcher and a defensive backfield that featured Nate Clements and Lawyer Milloy.

"We had a good defense then, but I think depth-wise, that's what's really going to push us over the edge," Kelsay said. "First day, we are encouraged. We know we have great potential. But it's all for naught if you don't put the work in."

The Bills' defenders have plenty to shoot for in a bid to improve on last year's dreadful numbers. Buffalo allowed a franchise-worst 5,938 yards, managed just 29 sacks -- 10 of which came in one game -- and gave up an average 27 points a game in contributing to the team's 6-10 finish.

The lack of a pass-rush has been a familiar problem. Buffalo hasn't averaged more than two sacks per game in a season since 2006, when they had 40.

Mario Williams, a two-time Pro Bowl selection and the NFL's defensive rookie of the year in 2006, and Anderson were brought in to help provide pressure.

At 6-foot-6 and 292 pounds, Williams' size and speed have wowed his teammates.

"He's a man-child," Jackson said.

And Williams' presence is what has Dareus giggling.

"He has to be the strongest guy I've ever met in my life," Dareus said. "Phenomenal football player, hands, feet. It's crazy. We're going to have fun this year, hee, hee, hee."