A list of defensive coordinator candidates quickly emerged after the Arizona Cardinals fired Bill Davis last week. That list has just as quickly diminished over the last few days.

Greg Manusky, who was the first person interviewed by head coach Ken Whisenhunt for the position, proved to be a hot commodity around the league. The former 49ers coordinator was not only courted by Arizona but also by Dallas Cowboys and San Diego Chargers.

Despite being a former teammate of Whisenhunt and assistant coach Russ Grimm in Washington, Manusky decided to join Norv Turner's staff in San Diego.

ESPN NFL Analyst John Clayton explained the move on Sports 620 KTAR's Doug and Wolf show Friday morning.

"The San Diego thing shouldn't be a surprise," the analyst said. "He worked with Wade Phillips when Wade was putting in the 3-4 defense there. It's a great place to live. He really had three opportunities. When Dallas started to warm up to him that was option number two and for whatever reason Arizona was number three. Maybe it was because there is so much more work to do."

Another name who has garnered much attention in the Cardinals coordinator search is Pittsburgh Steelers linebackers coach Keith Butler. Despite Butler's connection to Arizona's coaching staff he too may no longer be a candidate.

"He's not an option because I don't think [Pittsburgh] is going to let him out," Clayton said. "The idea is that he's eventually going to take over for Dick LeBeau. That's not going to be like Joe Paterno. Dick's not going to be there till he's 84-years-old. He's in his 70's right now and they want him to be the next guy on that defense."

With two of the team's top candidates no longer options, where will they turn to find a defensive coordinator? Clayton say that an answer might be difficult to find.

"It's going to be tough right now," he said. "You start to run out of defensive coordinators when you get all the jobs starting to close. The Raiders is the only open job for head coaches. Now the scramble really begins."

Although finding a coordinator may be becoming more challenging by the day, Clayton did have one surprise name to add to the mix.

"I wonder if they don't make a move on Rob Ryan," he said. "But he made a quick beeline down to Dallas now that Manusky turned them down so that could be an option. I know Al Davis gave him a call earlier this week either to talk head coach or defensive coordinator. Rob I think is a very viable option but they have to move fast."

Ryan, the former Browns defensive coordinator, could be quite the interesting choice for the team seeing as his father happens to be former Cardinals head coach Buddy Ryan. Buddy, who coached the team for the 1994 and 1995 seasons, left the franchise in quite the tumultuous way. He was fired the day after leaving the field before his final game, a Christmas night affair against the Cowboys, had concluded.

Listen to ESPN's John Clayton on Doug and Wolf