From ProFootballTalk.com:

REX RYAN A CHARGERS CANDIDATE

One name that quickly has emerged as a potential candidate for the sudden vacancy in San Diego is Ravens defensive coordinator Rex Ryan.

Ryan, the son of former Eagles and Cardinals coach Buddy Ryan and the twin brother of Raiders defensive coordinator Rob Ryan, has spent the last eight years with the Ravens. He replaced Mike Nolan as defensive coordinator when Nolan was hired by the 49ers.

Look for Ryan to be one of the first guys interviewed for the job.
This was my first thought when I heard about the Schottenheimer firing. They run a 3-4 defense similar to ours, though far less aggressive. They have no in-house candidates left to vie for the position, and a re-tread who washed out elsewhere (like Dennis Green or Jim Fassel) isn't going to be very appealing.

I'm sure Ryan will leave us for a head coaching job someday... but hopefully we can hang on to him for a little while longer. Say, enough to win another championship or two. Having him depart, and possibly take other coaches with him, this late in the offseason... that would be a severe blow to our plans for the coming season.