Making an NFL roster is a numbers game, one where the odds are rarely in a player's favor.
Every NFL franchise will trim its roster from 90 to 53 by preseason's end. Take the 32 clubs in the league, multiply that by the 37 players cut by each team and you get a grand total of 1,184 NFL hopefuls looking for work.
One thousand one hundred and eighty four.
That's a number that will keep a vast majority of players from ever feeling comfortable with their standing on a depth chart.
That goes for members of the San Francisco 49ers as well.
"You can never relax," Keith Reaser said prior to a Week 3 preseason home game against the Green Bay Packers. "You've got to keep that edge and have the mindset that you're competing for a job every day, every drill."
Reaser has flashed consistently throughout the month of August. His pass breakups came almost daily during training camp, and he's been credited with one pass defended in each of the first two preseason games.
The 49ers cornerback entered the offseason program under the radar. Reaser spent his entire rookie season in 2014 recovering from an ACL injury. The corner played in 13 games in 2015, but most of those reps came on special teams.
Reaser admitted that he welcomed a fresh start with the new coaching staff brought in by Chip Kelly.
"I was excited for the new staff; a clean slate just to show what I can do," he explained.
To those just familiarizing themselves with the former fifth-round pick, Reaser wants you to know that he's capable of being a complete corner in San Francisco's defensive backfield.
"I feel like I can do it all," Reaser said confidently. "I'm going to compete. I've got speed. I can tackle. I'm going to make plays on the ball at any time."
Reaser displayed those traits in last Saturday's game against the Denver Broncos. Mark Sanchez challenged him twice in the end zone during the second quarter. On the first of the two, Reaser kept up with Broncos up-and-coming wideout Cody Latimer on a go route from the 19-yard line.
The corner traced Latimer up the right sideline, fought through an offensive pass interference and made a diving play to bat down the ball.
"That's your chance to make a play," Reaser said. "I enjoy it when they throw the ball my way."
Reaser's study habits gave him an inclination that Denver would test him.
"From watching film, you learn that they like to take shots to the end zone once they get around the 30-yard line," Reaser said. "I was anticipating that was what they were going to do. I made sure I rerouted him at the line.
"I could tell from how hard he was running that he was going vertical. My next step was to cut him off."
Jimmie Ward and Tramaine Brock have held down the starting cornerback spots since camp opened. Defensive coordinator Jim O'Neil, however, warned on Monday that no starting job is safe. The coach named Reaser as one of the defensive backs on the roster who "is coming."
"I'm going to control what I can control," Reaser said. "I'm going to keep making plays. Whenever I get my opportunities, I'm going to capitalize on them. That's all you can do."
