Safety Da'Mon Cromartie-Smith, seen here as a Pittsburgh Steeler last season, joined the Redskins at training camp this weekend in Richmond. (Tom Uhlman/Associated Press)

There’s no time for new employee orientation amid the roster shuffling in the NFL preseason. There’s scarcely time to strap on a helmet.

The moment it becomes clear a player isn’t cutting it or his body breaks down, another is brought in.

In the fine-tuning of rosters for the regular season opener, the game clock never stops ticking for NFL general managers, scouting departments or the out-of-work players hoping to get their calls.

The past 48 hours in the life of Da’mon (pronounced DAY-mon) Cromartie-Smith are a case in point — a window on how quickly fortunes rise and fall during the NFL preseason, a three-week span of two-a-day practices designed to weed out the infirm among bloated, 90-man rosters so that the 53 who survive the final cut are the most skilled and durable among them.

Cromartie-Smith, a 6-foot-2, 203-pound safety who latched onto the Pittsburgh Steelers as an undrafted free agent in 2010, was in his 10th month of unemployment when he got a call last week from the Washington Redskins, inviting him to Richmond for a workout.

In a five-hour span Saturday, Cromartie-Smith auditioned on the field, signed a contract, had his hyphenated last name affixed to a No. 23 jersey and was tossed into a two-hour practice.

“Everything was pretty much going fast-forward — getting the gist of things, learning the terminology,” Cromartie-Smith said of his first day. “I’m kind of used to the scheme because we ran something similar up in Pittsburgh. And I had a lot of time to get my body right and mind right, so I was ready to come in and play whenever I was called on.”

Since Redskins training camp got underway July 23, four players have been let go and another four brought in and signed. These players who live on the fringes of NFL teams typically depart and arrive without fanfare, their names appearing in tiny newspaper print, if at all, as if commodities traded on the open market.

Some will serve as human tackling dummies for a time; others will play out full seasons.

It’s a cycle that plays itself out at every NFL camp: One player’s failure creates an opportunity for another.

And it’s the job of the Redskins’ scouting department to keep up with the daily comings and goings — not just throughout the NFL but in the Canadian Football League as well.

Former North Carolina State guard Alex Santos runs the department, which consists of three pro scouts and an intern. Each is assigned specific teams to monitor. All watch tape and collectively weigh in on prospects that should be put on the “ready list.”

So when Coach Jay Gruden and his staff cut cornerback Peyton Thompson the morning after his shaky performance in Thursday’s preseason victory over New England, General Manager Bruce Allen contacted Santos to say the team needed a safety.

Cromartie-Smith was the top safety on the list.

If the name sounds familiar, it’s because he’s a cousin of NFL cornerbacks Antonio Cromartie and Dominique Rodgers-Cromartie.

But pedigree counts for little in the NFL’s trenches, the ultimate meritocracy.

“He had two accrued seasons and was somewhat of a known player,” Santos said. “He’s not a rookie but was still a young player who was on the street.”

It also helped that Cromartie-Smith, 27, had played for Dick LeBeau, whose Steelers defense is similar to that of the Redskins.

So the Redskins called his agent to make sure he was available and healthy.

Yes. And yes.

After being waived by Pittsburgh in October, Cromartie-Smith returned to his home in Riverside, Calif., where he made a full-time job out of training his football-playing nephews, one of whom is headed to the University of Texas El Paso this fall.

“I was trying to keep up and do as much footwork and drills that would keep me up to speed,” Cromartie-Smith said.

When the Redskins’ call came, he packed his size 13 cleats, hopped on the flight the Redskins had arranged and landed at Richmond at 11 p.m. on Friday.

By 12:30 p.m. Saturday he was on a practice field running 40-yard dashes for Allen and defensive backs coach Raheem Morris. That was followed by footwork and agility drills.

“He ran around good at the workout, so we thought it was important to give him an opportunity,” said Gruden, who also liked his size.

Working with the third-team defense, Cromartie-Smith was shadowed on nearly every drill by Morris, who shouted instructions and encouragement with each step. During plays he wasn’t involved in, he stood with veteran Ryan Clark, a former Pittsburgh teammate, who translated the Redskins’ defensive verbiage for him.

After getting a copy of the Redskins’ playbook Saturday night, Cromartie-Smith was back on the field Sunday, with Morris hollering about footwork and pad levels.

“That’s a great job!” Morris yelled after the new safety made a play against wide receiver Rashad Ross.

And they shared a high-five.

“A lot of guys that are on the street that have had NFL experience all want to get back into the NFL,” Santos said. “For all of ’em, it’s a childhood dream, first of all. And to have it taken away from you, whether it’s due to injury or is just a numbers game, is tough. He in particular was very hungry and excited to come and work out for us.”