Of all the non-manual labor jobs out there, there can’t be any more difficult than that of a substitute teacher.

Can you imagine Aqib Talib and Derek Wolfe, when they were in fourth grade and a substitute teacher walked in?

When the regular teacher, Gary Kubiak, was out sick this week, the Denver Broncos called in Joe DeCamillis to substitute. His class is filled with NFL players whose assignment is to beat the rival San Diego Chargers this week.

What substitute teachers are to schools, interim head coaches are to the NFL. There are similarities in the challenges.

“It’s really not your team,’’ said Wade Phillips, the Broncos’ defensive coordinator who’s had previous interim gigs with New Orleans, Atlanta and Houston. “You’re part of that team, but you weren’t the head coach in training camp and all those things.

“Really, the interim guy just tries to get the guys to play as hard as they can play and keep them motivated. It’s usually when teams are doing bad. I’d like to be an interim coach when you’re undefeated. That’d be great. But most of the time it’s because something hasn’t gone well so you try to keep the team’s spirit up. This is different, obviously.”

Broncos general manager John Elway, in consultation with Kubiak and chief executive officer Joe Ellis, picked DeCamillis, Denver’s special teams coordinator, instead of Phillips or offensive coordinator Rick Dennison.

Was Phillips disappointed?

“No, not at all,’’ he said. “If you look at my interim record, I’d say, ‘Make sure you don’t make him the interim guy.’ I told you I was a lousy head coach anyway, especially as an interim head coach.’’

Phillips is 3-7 as an interim head coach, but an impressive 79-57 as a full-timer.

“I think it makes the most sense for Joe D because we’re involved in offense and defense, Rick and I, so it’s easier for him to do that,’’ Phillips said. “Plus, I’ve known Joe D for a long time and I really think he is a head-coaching candidate. I don’t know why he hasn’t been. John Harbaugh did it as a special teams coach. Joe’s been recognized as one of the best, or the best, for a long time at what he does as a coordinator, so it’s good for him.’’