Rob Ryan arrived in St. Louis on Friday. Will it be merely a weekend visit? Or his new residence as defensive coordinator of the Rams?

Ryan will interview today with coach Jeff Fisher for the coordinator's job that was supposed to be held last season by Gregg Williams, before Williams' indefinite suspension by the NFL for his role in the New Orleans "Bountygate" pay-for-performance scandal.

There were erroneous reports on Jan. 11 that Ryan already had been hired by Fisher. But that New York Post report may end up being correct after all — just a week or so premature. Fisher has been a longtime friend of the Ryan family dating back to his days as a player under Chicago Bears defensive coordinator Buddy Ryan in the 1980s.

Rob Ryan, 50, is one of Buddy's sons, as is New York Jets head coach Rex Ryan. Rob Ryan was fired less than two weeks ago as defensive coordinator of the Dallas Cowboys.

At one point this season, the Cowboys were fifth in the NFL in total defense, but as injuries mounted over the second half of the season they slumped to a final ranking of 19th. The Cowboys ended up yielding 5,687 yards — a franchise worst. In addition, Dallas produced only 16 turnovers, tied for 27th in the league.

Ryan spent the 2011 and '12 season with Dallas, preceded by two seasons (2009-10) as defensive coordinator in Cleveland, and five seasons (2004-08) as coordinator in Oakland. In those nine seasons as a coordinator, Ryan never was part of a team with a winning record and guided only one defense ranked in the top 10.

Before those coordinator stints, he was linebackers coach for Bill Belichick in New England and was part of the coaching staff that defeated the Rams in Super Bowl XXXVI.

Another factor to be considered is that the majority of Ryan's NFL experience has come on defenses that play a 3-4 front. The Rams play a 4-3, and as word leaked out about the Rams' interest in Ryan, some Rams defensive players wondered if the team was switching to the 3-4, which could mean substantial changes in personnel — or use of personnel.