You know the old idiom “those who can, do; those who can’t, teach.” 

Allow me to introduce Doug Pederson, Frank Reich and the 2015 Philadelphia Eagles coaching staff. 

The Eagles have eight coaches on their staff who played in the NFL. Those eight played a combined 1,038 games in the league, but have exactly zero Pro Bowl appearances. That means they were good enough to stick around, but never great. 

If we take it a step further, the two guys in charge of the Eagles’ offense, Pederson and Reich, both had lengthy careers in the NFL, primarily as backups. Of Reich’s 118 career games, just 20 were starts. Of Pederson’s 100 career games, just 17 were starts. 

Now, both have risen to an extremely high level in the coaching world. 

And they’re not alone. Cowboys head coach Jason Garrett was a backup in the NFL for eight seasons and Broncos head coach Gary Kubiak, who will lead his team into the Super Bowl next weekend, was a backup in Denver for nine seasons. 

So what is it about backup quarterbacks that make them good coaches? 

“I think from a backup’s perspective, you’re kind of the coach on the field to the starter,” Pederson said last week in Alabama for the Senior Bowl. “You see things differently. You’re not in this stressful role of being a starting quarterback. I think being a backup can help you. You’re processing the information just like a starter. It allows you to make decisions and really coach that starter on the football field.”

Pederson served as a backup quarterback for some notable names during his playing career: Dan Marino, Brett Favre and Donovan McNabb. When Pederson was brought to Philadelphia in 1999, his job was to mentor McNabb, who eventually overtook him as the team’s starter mid-season. 

Reid once said, via the Chiefs’ website, he knew Pederson would be a coach while watching the actions of Favre during a stoppage in Pederson’s second stint with the Packers. 

“I'll tell you when I really saw it — his second stint at Green Bay,” Reid said. “I watched [Brett] Favre come off the field and he went right to Doug. At that moment, I go, 'You know what? This guy. He can do this. He can be a coach.’”

Before he ever backed up Favre or McNabb, Pederson was with the Dolphins in the early '90s. The team even cut him a total of six times. But Pederson finally stuck with the Dolphins in 1993 and even helped Don Shula pick up win No. 325 to break the all-time record. 

"I’m happy for Doug,” said Marino, now in a special advisor role with the Dolphins, in a statement from the team. “I enjoyed sharing a quarterback room with him and saw first hand his knowledge of the game and his work ethic. I'm sure he will do a great job with the Eagles."

The thing Pederson, Reich, Garrett and Kubiak all have it common is that they were backups behind some all-time great quarterbacks. We know the guys who were in front of Pederson, but Reich played behind Jim Kelly, Garrett played behind Troy Aikman and Kubiak spent his entire career behind John Elway. 

So these future top-level coaches learned behind some of the greatest to ever play the game, but they themselves weren’t great. They were, however, smart enough to stick around the league for about a decade apiece. That doesn’t happen by accident. It happens because they have qualities that allowed them to overcome their physical limitations as players. 

Now, it’s those same qualities that have them finding success in the coaching world.