He was passed over in the 2012 NFL draft, and now is trying to beat the odds to make the Ravens' linebacker-stacked roster.
The Ravens will make their final set of cuts Friday, whittling the roster from 75 to 53 players.
Carr understands what is at stake, and so far the Ravens haven't had any complaints with the rookie on or off the field. The 6-feet-2, 247-pounder leads the team with a dozen tackles through three preseason games.
"I believe in second chances," Harbaugh said. "Nigel had to go to Alabama State and he played great for them. He was a model citizen, and he has been that here. We all learn lessons, sometimes the hard way. Especially guys that pay a heavy price for a mistake, you shouldn't have to keep paying a price."
Carol Brown describes herself as her son's rock, but she was worried that she would break down when he got arrested.
Once she heard Carr was in jail, she immediately made the nearly three-hour drive from her home in Jacksonville, Fla., to Tallahassee, Fla., to be with him.
"He knew that he made a horrible mistake," said Brown, a divorced single mother who works as a mortgage underwriter. "He said, 'Mom, I made a mistake that won't go away.' He cried, he was emotional, he was a nervous wreck.
"I was very concerned and worried. I didn't raise him that way. That's not who I am, that's not who we are."
Mortified by his transgressions, Carr said he had strayed from the religious base instilled by his mother. He grew up going to church and singing in the choir as a tenor.
"I knew I hurt her bad, I could see it in her eyes," Carr said. "I was ashamed and embarrassed."
Carr acknowledged that he got caught up in a fast lifestyle at Florida State, and a desire for material things. He wasn't an NFL player yet, but coveted the trappings of a professional athlete: cash, nice clothes and an expensive car.
"You think about that money," Carr said. "You want flashy things and get impatient. You lose sight of who you are. I did stuff that I saw growing up. Old, bad habits surface. I know I was wrong."
On that night two years ago, Carr was accused of smashing in a car window and driving away in a white Buick registered to his mother. The victim discovered her book bag, checkbook and purse in a large trash bin outside of Carr's apartment complex, and her credit card and sweater in his car.
Surveillance video captured a man in a white car throwing things into the bin, according to police reports.
He pleaded no contest to lesser charges of theft, a second-degree misdemeanor, in the burglary case and was sentenced to three years of probation and nearly $6,000 in fines and court costs. Carr said that he can end his probation early if he pays the remaining balance of $4,000.
If he makes the active roster, Carr would make a base salary of $390,000 and would be due a weekly game check of $22,491.
“I thought I ruined my life, but it was just starting,” Carr said. “I got brought down, I got humbled. One stupid mistake can cost you so much. At the time, it felt like something I couldn't get past.
"I thought I would be in jail. Now, I say, 'What the hell was I thinking?' It doesn't make no sense. I don't know why I did it."
Carr was an all-state linebacker at First Coast High in Jacksonville and earned Under Armour All-American honors as he recorded 399 career tackles. He emerged as a blue-chip recruit with a reputation for punishing opponents.
After playing as a true freshman at Florida State, Carr was named the Seminoles' most dependable linebacker the following spring. A prominent role as a starting strong-side linebacker awaited him until his arrest .
"If I had stayed at Florida State, I was on my way to becoming a star," Carr said.
Florida State coach Jimbo Fisher still laments the loss of Carr from the program He even allowed Carr to participate in the Seminoles' NFL Pro Day before the draft.
"He made bad choices, but I love Nigel and he paid a price," Fisher said. "I was almost devastated, I was sad. It shocked me. I take it personal. We have a great relationship. There was nothing I could do but help him find a new place to go. It was totally out of my hands.
"He has great instincts and energy. He has a passion. No doubt, he would have been drafted if you eliminate the character issues and he played at a high level. I'm tickled to death that he's doing well now."
Carr received a fresh start when he transferred to Alabama State, a historically black college in Montgomery, Ala., that competes at the Football Championship Subdivision level.
"When Nigel got here, he thought he had lost it all," said Alabama State coach Reggie Barlow, a former Pro Bowl return specialist with the Jacksonville Jaguars. "It was a humbling experience. He understood this was a second shot and not to blow it. I can't say enough positive things about him."
In two seasons at Alabama State, Carr registered 73 tackles, 9.5 for losses, three sacks and one interception and helped the Hornets win a Southwestern Athletic Conference division title.
Although Carr didn't excel academically at first, Barlow said he obeyed curfews, attended study hall and was well-behaved.
"I told [Ravens general manager] Ozzie Newsome we had zero problems with Nigel, he took care of business," Barlow said. "The Ravens do an outstanding job of knowing about those guys that fall through the cracks."
Motivated by fatherhood
Two weeks after Carr left Florida State, his girlfriend, Treana Ringer, gave birth to a baby girl named Ariana.
Since becoming a father, Ringer said Carr has become more responsible and is actively involved in his daughter's life. Ariana celebrated her second birthday on Aug. 9.
"He wants to be included in everything, he wants to help," said Ringer, who is in her final semester at Florida State. "He's being responsible. He's stepping up and doing a great job. I'm proud of him."
If Carr secures a spot with the Ravens, he plans to move Ringer and his daughter to Baltimore to be with him.
"I play for her, I play for my family," Carr said. "I've got to feed her. Right now, it's football that's going to do that. When she was born, I cried and I told God I wouldn't get in trouble again."
Listed third on the depth chart at middle linebacker, Carr has been soaking up knowledge from All-Pro Ray Lewis.
Praised by linebackers coach Ted Monachino for his aggressive style, Carr is hoping he's made a strong impression. Although prone to penalties, drawing a fine of $15,750 for a roughing the passer infraction for his hit on Detroit Lions quarterback Shaun Hill, Carr is an active, athletic presence.
If the Ravens aren't prepared to give Carr a spot on the final roster, he could be an ideal candidate for their practice squad. While Carr awaits his future, he said he's focused on keeping his word to Harbaugh.
"I'm proving that I'm a player here," Carr said. "Most of all, I'm proving I'm a good person who made mistake. The coaches love my personality, energy and passion. It's a blessing that this organization put their faith and trust in me."