GREEN BAY — When Green Bay Packers coach Mike McCarthy decided to do what an NFL source called his "due dilligence" in finding the team's new defensive coordinator, he wasn't kidding.

As much as Mike Nolan makes sense as McCarthy's top choice, his hiring is no longer the slam-dunk some NFL types believed.

One day after bringing his old boss, Nolan, in for an interview, McCarthy played host Friday to highly regarded veteran defensive coordinator Gregg Williams at Lambeau Field, an NFL source said.

Nolan, the former San Francisco 49ers coach who had McCarthy as his offensive coordinator in 2005, was considered the leading candidate to get the job, but Williams has emerged as a viable candidate as well.

And while McCarthy may want to get one of the two men signed, sealed and delivered before competition for their services escalates, the source said McCarthy may also wait until several playoff teams finish their seasons this weekend, just to keep his options open.

McCarthy did the same thing the first time he hired a defensive coordinator, interviewing four candidates in 2006 before promoting Bob Sanders, who'd been the defensive line coach under Jim Bates on Mike Sherman's 2005 staff. Sanders was fired Monday, along with four position coaches and strength and conditioning coach Rock Gullickson.

Williams, who spent last season as the Jacksonville Jaguars' defensive coordinator but was not retained by coach Jack Del Rio, interviewed with the New Orleans Saints on Thursday and is also being pursued by the Houston Texans.

Williams, the former Buffalo Bills head coach, has impressive credentials, having had successful coordinator stints with the Tennessee Titans and Washington Redskins.

However, he won't be inexpensive, having once been the highest-paid assistant in the league under the Redskins' Joe Gibbs. Nolan, meanwhile, could come cheaper since the 49ers still owe him following his firing in October.

Attempts to reach Williams' agent, Marvin Demoff, on Friday were unsuccessful.

McCarthy also has spoken by phone with another of his former bosses, Jim Haslett, about the job. Haslett, the ex-Saints coach who had McCarthy as his offensive coordinator from 2000 through '04, was the St. Louis Rams' interim coach this season and is still a candidate for the Rams job.

The NFL source said McCarthy may still speak to an up-and-coming defensive coach or two before making a decision. One such coach is Philadelphia secondary coach Sean McDermott, whom McCarthy can't interview until the Eagles' season is over. The Eagles face the defending Super Bowl-champion New York Giants in an NFC divisional playoff game Sunday.

McDermott was named secondary coach this season after coaching the Eagles' linebackers in 2007 and serving as Andy Reid's secondary/safeties coach from 2004 through '06. He is a disciple of Eagles coordinator Jim Johnson's aggressive, blitz-heavy scheme, which ex-Eagles assistant and current Giants coordinator Steve Spagnuolo also uses.

Meanwhile, although it appears hiring a defensive coordinator is McCarthy's top priority, another NFL source said McCarthy intends to interview Oakland Raiders special teams coach Brian Schneider for the special teams coordinator opening created by Mike Stock's retirement.

Schneider interviewed with the Jacksonville Jaguars earlier this week and is also a candidate for the Seattle Seahawks' position.

It remains unclear whether Packers assistant special teams coach Shawn Slocum will move up to the special teams coordinator spot or be promoted to a position on defense. Slocum coached linebackers and defensive backs in the college game and is thought to prefer coaching on defense.

Slocum could be a candidate to take over as the Packers' linebackers coach if assistant head coach/linebackers coach Winston Moss departs for another job or becomes the team's defensive coordinator.

Moss, who interviewed for the St. Louis Rams' head-coaching position last week, is set to interview with the Oakland Raiders this weekend for their head-coaching job. Raiders interim coach Tom Cable, who took over following Lane Kiffin's early-season firing, is expected to have the interim tag removed and get the job, but Moss did play for the Raiders from 1991 through '94 and has some relationship with owner Al Davis.

If Cable gets the job, his defensive coordinator could be ex-Packers coordinator Ed Donatell, who was the Packers' coordinator from 2000 through 2003 and Atlanta's coordinator from 2004 through '06.

The Raiders are in the market for a defensive coordinator after Rob Ryan left the team to serve on Eric Mangini's staff in Cleveland. Donatell, who spent last season at the University of Washington, worked with Cable years ago at the University of Idaho and with the Falcons in 2006.

Another former Packers coach, cornerbacks coach Lionel Washington, is a candidate to be the Raiders' secondary coach. Washington, who coached with the Packers from 1999 until being fired earlier this week, played for the Raiders from 1987 through '94 and again in '97.