From Jim Thomas of The St. Louis Post Dispatch:

Jason Garrett, the assistant head coach-offensive coordinator of the Dallas Cowboys, is the so-called “mystery” candidate in the Rams’ head-coaching search, league sources told the Post-Dispatch on Monday. Barring an unexpected complication, Garrett will interview Wednesday in Los Angeles as one of the Ram’s finalist interviews.

According to league sources, the Rams have settled in on five finalists: current Rams coach Jim Haslett already has taken part in his finalist interview last week in L.A.; Minnesota assistant head coach-defensive coordinator Leslie Frazier is scheduled to interview there Tuesday; and it has now been confirmed that Steve Spagnuolo of the New York Giants will interview in Los Angeles on Thursday. (The Giants have granted St. Louis permission to speak to Spagnulo.)

The fifth finalist is Baltimore assistant head coach-defensive coordinator Rex Ryan. The only reason why Ryan was interviewed in Baltimore Sunday instead of in Los Angeles is because the Ravens are still alive in the NFL playoffs. Whether the Rams can afford to wait on Ryan, particularly if the Ravens win Sunday, remains to be seen.