ST. LOUIS — St. Louis Rams head coach Steve Spagnuolo is likely to return to Philadelphia to become the Eagles’ defensive coordinator if, as expected, he is fired at the end of the season.

Spagnuolo, an Eagles assistant from 1999-2006, is “all but certain” to replace first-year coordinator Juan Castillo in Philly as Rams owner Stan Kroenke clears the deck in St. Louis, the San Diego Union-Tribune reported. Spagnuolo left Philadelphia to become the Giants defensive coordinator.

The 52-year-old’s reputation boomed after helping to mastermind the Giants’ shock victory over the undefeated New England Patriots in Super Bowl XLII, has led St. Louis to only 10 wins in his first three seasons as a head coach.

The same report suggests Kroenke will also fire general manager Billy Devaney and move for A.J. Smith, should the Chargers GM be fired by San Diego along with head coach Norv Turner.

But the newspaper quoted league and agent sources as saying Smith will end his association with Turner to instead hire ESPN analyst Jon Gruden as his head coach should he be hired as Rams general manager.

Sources said that Gruden, the former Tampa Bay Buccaneers and Oakland Raiders head coach, plans to return to the NFL next year despite signing an exclusive five-year contract with the sports network in October, which is scheduled to begin in September 2012.