Many who watched free safety Pierre Warren work through the beginning of his first pro training camp at The Greenbrier resort in the mountains of West Virginia with the New Orleans Saints this summer figured he could one day start in the NFL.

But no one can claim — believably — they foresaw Warren making his debut in the league and for the Saints as a starting free safety under the circumstances he did in New Orleans’ 34-27 loss to the Baltimore Ravens at the Mercedes-Benz Superdome on Monday night.

That’s because at the end of August the Saints were so loaded at safety they had the luxury of being able to cut Warren — and they did.

Times could not have been more different Monday.

Six days after Warren rejoined the Saints (4-7) and New Orleans lost its third safety for the remainder of the 2014 season with a major injury, he made an impact by forcing a fumble feet away from New Orleans’ goal-line and scooping it up to prevent a score.

Hailing from Alabama’s Jacksonville State, a Football Championship Subdivision school, Warren began camp in a fashion any player would be proud of. He broke up passes, intercepted them and knocked the ball out of opponents’ grasps in drills at training camp. He almost picked off a throw in the preseason opener.

But as camp phased back to New Orleans, the Saints gave a significant look to safety Marcus Ball, who spent 2012 and 2013 with the Canadian Football League’s Toronto Argonauts. Though Ball missed the last two exhibition games with a hamstring injury that sidelined him through the end of September and Warren intercepted an overthrown pass in the preseason finale (coincidentally, at the Superdome against the Ravens), the 22-year-old did not crack the first 53-man roster. New Orleans went with three-time Pro Bowl safety Jairus Byrd; 2013 first-round draft choice Kenny Vaccaro; fourth-year pro Rafael Bush; Vinnie Sunseri, the rookie out of Alabama; and Ball at safety.

The Saints sent Warren to their 10-man practice squad. He lasted 17 days there before an injury to a linebacker forced them to bring in another player at that position to the practice squad to not compromise depth during mid-week team drills. Warren was unemployed for 19 days before latching onto the Minnesota Vikings practice squad, and he remained there for the next six-plus weeks.

It might have been much longer. But Byrd tore a meniscus in a practice before an Oct. 5 Saints win in New Orleans. Sunseri broke his left forearm in a defeat at home against San Francisco on Nov. 9. And Bush fractured his right fibula at the Superdome in a loss to Cincinnati on Nov. 16.

Byrd, Sunseri and Bush all landed on the Saints’ season-ending injured reserve. The Saints were left with safeties Vaccaro, Ball and Jamarca Sanford, who had played with the Vikings from 2009 to 2013 but was acquired by New Orleans as a free agent after Sunseri went down.

That was a major problem. None among Vaccaro, Ball or Sanford were in the mold of free safeties Bush or Byrd.

But Warren was. He had also spent the entire preseason learning the Saints defense. So the Saints front office signed him away from the Vikings’ practice squad, brought him to New Orleans in time for practice Thursday.

Saints coach Sean Payton on Monday said his staff deployed a number of combinations before facing the Ravens. Payton said, “Those guys all got a lot of work (in the) week at the free safety position, and really it was not ... decided on until the latter part of the week.”

At the conclusion of that process, one thing was clear.

“We felt like (Pierre) gave us the best opportunity at free safety,” Payton said.

So the Saints front office signed him away from the Vikings’ practice squad, brought him to New Orleans in time for practice Thursday — and tasked him with starting for the first time in his career four days later, with the world watching him on “Monday Night Football.”

Warren’s welcome to the big show arrived early. He ran across the field to make a tackle at the end of a 38-yard run by Ravens running back Justin Forsett that could’ve gone for a touchdown on Baltimore’s first play from scrimmage. The Ravens (7-4) later scored, a touchdown but the effort was solid.

Then, on the Ravens’ third offensive drive, aside from helping to put a stop to a 26-yard run, he met Kyle Juszczyk head-on at New Orleans’ 1 after the Baltimore fullback caught a pass. Warren wrapped the fullback up, ripped the ball out, recovered it, and denied the Ravens an easy score — a highlight during a first half that had the Saints ahead 17-14.

Ultimately, Warren tied for the Saints’ lead in total tackles with seven.

It wasn’t enough to prevent the Saints from losing a third-straight game in New Orleans. It wasn’t enough to prevent him from missing a tackle on a 13-yard, third-quarter touchdown run by Forsett.

Afterwards, Vaccaro said he’d have to watch the film before evaluating Warren’s -- or any other -- performance on defense. Warren didn’t wait around to speak with reporters after the game.

Yet the rookie did as much as could be reasonably asked with one of the hardest assignments a young pro could be given his first time up.