From 2004-06, he served as the Philadelphia Eagles' linebackers coach. In 2007, he became the Giants' defensive coordinator, where we won the Lombardi Trophy with Big Blue and coached against Manning every day.
Spags has remained in the NFC since 2009, when he took over as the St. Louis Rams' head coach, and this year, he'll be reacquainted with his former quarterback as the New Orleans Saints' defensive coordinator.
As coach of the Rams, Spags faced Manning just once -- a Week 2 meeting in 2011. In that game, Manning threw for 223 yards and two touchdowns en route to a 28-16 victory.
Despite the ongoing debate about whether Manning is or is not an elite quarterback in the NFL, Spags believe he is one of the best.
"There aren’t many that are elite, he’s one of them. He’s another one of those guys," he said.
"He is the kind of guy that doesn’t get rattled. He sits big in the pocket. People will say he’s not a scrambler, yet you can always find some plays in a game where he gets himself out of trouble, puts the ball downfield right on somebody and makes a big play. We have to be prepared for everything."
Spags will get another opportunity to face Manning on Sunday, as both teams make a push for the post-season.
Facing his former team, the Saints' DC said, is always a special feeling.
"It's kind of like playing your brother, sometimes you compete harder when you're out on the basketball court and you go out and compete against your brother," he said.
Follow Sam on Twitter @SamSpiegs