Just under two weeks on from firing Steve Wilks, San Francisco 49ers head coach Kyle Shanahan finally shed some light on their defensive coordinator search.

He revealed to NBC Sports Bay Area's Matt Maiocco that the 49ers had interviewed former Los Angeles Chargers head coach Brandon Staley and an internal candidate in Nick Sorensen, San Francisco's defensive pass game specialist/nickels coach. Shanahan confirmed he is also set to interview 49ers defensive backs coach Daniel Bullocks. In addition to Bullocks, the 49ers must interview one more minority coach for the position to comply with the Rooney Rule.

But in providing an extensive update on the search, Shanahan also kept some mystery alive.

Indeed, Maiocco reported that Shanahan told him he is likely to interview two further external candidates, though he did not reveal the identity of those coaches.

That is where the mystery lies.

It's unclear why those candidates' names are being kept secret, but it's easy to speculate that Shanahan could be keeping his cards close to his chest because the interviewees are of such a stature that neither potential hire would want their candidacy to be public knowledge.

Two potential blockbuster names who would probably rather have the interview process be conducted in secret: Pete Carroll and Bill Belichick.

Carroll considering returning to the team for whom he last served as a defensive coordinator back in 1996, just over a month on from parting ways with the Seattle Seahawks, would generate massive headlines. Belichick being a candidate following the end of his storied tenure with the New England Patriots would be one of the biggest stories of the year and generate a media circus.

Neither the 49ers, nor Carroll, nor Belichick would want that kind of attention around the process.

It's debatable whether Carroll or Belichick would even be interested in being a coordinator again after both enjoyed such prolonged success as head coaches. However, until the 49ers tell the world otherwise, there is the possibility that two of the greatest coaches of the previous two decades — and, in Belichick’s case, NFL history — are indeed in the mix to take over one of the best defenses in the league. 

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