NEW ORLEANS — The New Orleans Saints hired Gregg Williams to fill their vacant defensive coordinator's post, hoping he'll shape up a unit that allowed 339.5 yards per game.

Coach Sean Payton announced the hiring Thursday, a little more than a week after the Saints fired former defensive coordinator Gary Gibbs.

New Orleans ranked 23rd in the NFL in total defense during the 2008 regular season, Gibbs' third season with the Saints.

Williams, who spent three seasons as a head coach in Buffalo earlier this decade, spent 2008 as the Jacksonville Jaguars' defensive coordinator, but it was a down year by his standards. Jacksonville's 331 yards per game ranked 17th in the league. The unit allowed 22.9 points per game, which was 21st in the NFL.

In five of the last nine seasons, however, Williams' defenses have ranked in the top 10 in the league, including three top threes.

"A lot has gone into this decision, and we targeted Gregg as the coach we'd like to hire after our first interview because he was so impressive and prepared," Payton said. "As an offensive coach, I have game-planned against his defenses in the past, and I know the problems they create. He's an aggressive coach, but his units are always sound fundamentally. We have some pieces in place for him to work with, and I know he's excited to get started."

Williams spent four seasons as assistant head coach and defensive coordinator with the Washington Redskins (2004-07). Before that, he was the Bills' head coach for three seasons (2001-2003) and defensive coordinator in Tennessee for four seasons (1997-200).

In his first season with the Redskins, Williams' unit ranked third in the NFL and first in the conference. The next season, Washington's defense ranked ninth in the NFL and sixth in the NFC.

In 2003, Buffalo's defense was second in the NFL with Williams as head coach. In 2000, when Williams was defensive coordinator for Tennessee, the Titans' defense ranked first in the NFL.

"Gregg is a tremendous addition to our coaching staff," general manager Mickey Loomis said. "We were looking for a coach with experience, a proven track record of success and a clear philosophy on where the improvements needed to be made on our defense and that process."

The Saints' defense has been a weakness since Payton, a former quarterback who calls the team's offensive plays, took over in 2006. In 2008, the Saints led the NFL in total yards per game (410.7), passing (311.1) and points scored (28.9), while Drew Brees became only the second player in league history to pass for more than 5,000 yards. But New Orleans finished 8-8, missing the playoffs for a second straight season in large part because of a defense that gave up too many big plays in the late stages of close games.

The Saints' defense was hampered by injuries. By mid-November, the unit had lost starting cornerbacks Mike McKenzie and Tracy Porter, as well as starting defensive end Charles Grant, to season-ending injuries.

Still, the Saints are hopeful that all three players will come back next season, solidifying a unit led by defensive end Will Smith, standout rookie Sedrick Ellis and middle linebacker Jonathan Vilma.

Vilma is a free agent, but has said he would prefer to stay in New Orleans, where he never missed a defensive snap in 2008 and led the team in tackles. The Saints have said they intend to re-sign him.

With no glaring needs on offense, the Saints also could choose to use top picks on defensive players in this spring's NFL draft.