Singletary made his name as a linebacker with the Bears. Although he has been successful in his brief coaching stints with the Ravens and 49ers, he has never been a head coach or even a coordinator at the professional level.
The Chargers also arranged to meet with Ron Rivera, the Bears defensive coordinator and one of the hottest candidates left on the market. In fact, Rivera would likely be a head coach elsewhere were it not for the Bears' Super Bowl run. His biggest drawback is his lack of familiarity with the 3-4 defense.
One coach plenty familiar with that scheme is Mike Zimmer, who spent the last six seasons as the Cowboys defensive coordinator. Zimmer ran a scheme similar to that in place in San Diego during the last two seasons in Dallas.
Zimmer is now a coordinator on the Atlanta staff, which was reshuffled when Jim Mora was fired. Mora, too, is a confirmed candidate for the Chargers' vacancy. Mora posted a 26-22 record during three seasons in Atlanta, taking the Falcons to the championship game during his first year on the job.
Then there is Gary Gibbs - the Chargers have requested permission to speak with Gibbs but there was no word on whether the Saints are prepared to allow their assistant to pursue the opening.
The final verified candidate for the time being is Rex Ryan, the defensive coordinator in Baltimore. Ryan has held that post for the last two seasons, with the Ravens defense ranking in the top five both years.
The list of candidates could continue to grow with names, although the Chargers would like to make their selection as quickly as possible. The release of Marty Schottenheimer came abruptly and his eventual successor could come to the forefront just as suddenly.