The one thing you can predict with certainty as the Eagles begin a remarkable week of action – preseason finale, roster cuts, establishment of practice squad, opener to NFL season – is that it will be unpredictable because, well, it always is unpredictable. Every roster spot matters. The practice squad is chosen with great care. Trades are weighed with careful consideration.

So, in the next week, the Eagles are going to become a roster. It's going to change as the Eagles work the waiver wire (although, as Super Bowl Champions, they have the 32nd and final claim position in the NFL), make a trade or two or three and churn the bottom of the roster during the season.

But it all begins with this preseason game as the Eagles keep their eyes on the players at Lincoln Financial Field on Thursday night as well as the other 15 games around the NFL.

"You play every game knowing that you're auditioning for a job," linebacker Nathan Gerry said. "There are 32 teams in the league, and you want somebody to want you. Every play matters. There's a lot of pressure, but that's what this league is all about. You have to perform. If you go out there and do your job, somebody is going to notice."

Gerry is an example of using the practice squad to advance a career. A fifth-round draft pick last year, Gerry was initially cut as the Eagles reduced the roster to 53 players. He was added to the practice squad once he went unclaimed, worked hard, kept his head down, and in mid-October was promoted to the active roster. Gerry was with the Eagles through the Super Bowl, gained valuable experience, and now figures to gain playing time at linebacker, likely on the weak side, as well as being a major contributor on special teams.

"Being on the practice squad helped me. I was still in the classroom and at practice. I became a better football player. I learned the scheme," he said. "It was tough not playing on gamedays, but it motivated me. It ended up being a positive experience."

The Eagles traded for defensive end Michael Bennett in the spring, using a draft pick and wide receiver Marcus Johnson, a former member of the practice squad, to send to Seattle. Third-string quarterback Nate Sudfeld, who has been so impressive this summer and whose career arc is heading in a positive direction, was acquired from waivers last year after his release from Washington and began his Eagles career on the practice squad.

The NFL has legions of practice-squad-players-turned-valuable-active-roster players throughout it. Much of what the Eagles see in this preseason finale against the Jets (7 p.m., NBC Philadelphia) is going to help shape the vision of the practice squad.

"I'm in a position where I just want to go out there and execute the offense and have fun," said quarterback Christian Hackenberg, who has practice squad eligibility. "I think my performance helps dictate my future. I'm only 23 years old. I've got a lot of football left to play in my lifetime."

Joe Callahan, who along with Hackenberg is expected to see a lot of snaps against the Jets, knows the business. He wasn't drafted after a great career at Division III Wesley (Delaware) College and then earned a contract from the Green Bay Packers, saw a lot of playing time in the 2016 preseason, and made it to the team's 53-man roster. Then he was waived and signed by the Saints. Then he was let go a week later and signed by Cleveland.

Callahan was waived by the Browns after a month and signed to Green Bay's practice squad a few days later. He spent the remainder of 2016 on Green Bay's practice squad and then stayed with the Packers through the summer of 2017 before being released as the Packers reduced the roster to 53 players. Callahan was not claimed by another team and was signed to the Packers' practice squad last September, where he remained until Aaron Rodgers was injured. Callahan then became the No. 2 quarterback in Green Bay and even took some regular-season snaps in the final game of Green Bay's season.

Perseverance is essential in this business.

"You never know what's going to happen. That's probably the number one lesson I've learned in the NFL," Callahan said. "You can't lose your focus or get caught up thinking about numbers. You just have to do your work, don't take shortcuts, and do the best you can do when you step out on the field. It's a pretty hectic time right now. Just go out and play and do what you love to do, and that's play football."

And that's what the Eagles will do on Thursday night against the Jets. The starters will be on the sidelines, shoulder pads off and as relaxed as they will be all season. Once the game ends, another season begins – the roster-manipulating season – as the Eagles also set full sights on the Atlanta Falcons and the September 6 opener. After all of these months, it comes down to the wire with the 2018 season just days away.