Nick Caserio has aced the fill-in act before.
As a freshman quarterback at John Carroll University in the mid-1990s, Caserio entered the season No. 2 on the depth chart, but was soon thrust into the top spot when the senior starter sustained a season-ending injury.
"He never gave up the position, was a starter the rest of the way, and ended up setting a number of passing records for us," recalled Tony DeCarlo, the head coach at the time. "If one thing stood out from that time, it was his tremendous work ethic."
Caserio is now in line for another move from No. 2 to No. 1, and his present employers - the New England Patriots - surely hope it goes as well as it did back at John Carroll.
The 33-year-old Caserio, who has served as the Patriots' director of player personnel since last February, is expected to assume more responsibility in the front office after vice president of player personnel Scott Pioli's departure to Kansas City as general manager.
So, Patriots followers might ask, who is Nick Caserio?
A native of Lyndhurst, Ohio, he joined the Patriots in 2001 as a personnel assistant, bolstered by the recommendation of his former college teammate, Josh McDaniels. His time with the Patriots has zigzagged - he worked as an offensive coaching assistant (2002), then as an area scout (2003), was director of pro personnel (2004-06), then returned to the sideline as wide receivers coach (2007).
Caserio was moved back to the front office last February, perhaps with the thought that if Pioli finally did depart, an in-house replacement would be in place, already learning on the job.
Caserio's thirst for learning football, it turns out, goes back to his high school days at University School, a private school in the suburbs of Cleveland.
"Football is his passion," said Joe Perella, who coached Caserio for eight years, first at University School, then at John Carroll. "He was a kid you had to tell to stop, whether it was in the weight room, on the field, running. He'd just keep going, a total perfectionist.
"He's the hardest-working kid I've ever coached."
That extended to his days at John Carroll, where he beat out McDaniels at quarterback, leading the coaches to move McDaniels to receiver.
"He was someone we had to kick out of the office, that's how committed he was. Nick couldn't watch enough film in preparing himself," DeCarlo said. "It was just unbelievable, and got to the point where the assistant coaches had to go up to him and say, 'Nick, get out of here.' "
Both Perella and DeCarlo recalled that Caserio's film study helped him understand what the opposition was doing, and at quarterback, he'd often switch the play based on what he saw before the snap.
"He was the only kid that I could rely on in a checkoff system; I never had anyone else do that," Perella said. "He's one of sharpest kids I've dealt with."
That type of work ethic, headiness, and passion for football helped Caserio carve out a niche under Bill Belichick. His NFL career progression - flip-flopping between scouting/personnel and coaching - should aid him in his role because part of what made the Belichick/Pioli pairing work so well was that Pioli knew the type of player Belichick sought, and effectively communicated that to scouts.
From having sat in on coaching meetings, Caserio also should have a similar knack for finding the right players for the system.
"I've always been very, very impressed with Nick's ability to adapt, and I think it speaks volumes to his ability to buy into Bill's system and being a team guy and doing whatever it takes to help the team win," said Atlanta Falcons GM Thomas Dimitroff, the former director of college scouting for the Patriots.
"Nick has always risen to the occasion when asked to fulfill a task for Coach Belichick. I think it's been invaluable for his development as a budding executive in this league. He's obviously well-rounded on the coaching side and personnel side, and it's very rare to see that."