That remarkable stretch of 160 consecutive games could come to an end in three weeks. It's not because of injury. It's not because of his performance. In some part, it's because of his unselfishness.
Humphrey, a first-round pick from a year ago, credits his development to the first time he sat down and talked with Carr in a sauna. Carr broke down the route tree a wide receiver can run after he goes 5 or 10 yards downfield, revealing how certain players can tip off their comeback and fade routes.
"I used to just guard guys," Humphrey said. "But [Carr] showed me there are a lot of things you can think about when it goes down that will help your chances."
In a city that knows something about ironmen (think Cal Ripken Jr.), Carr is the epitome of toughness, hard work and class. One team official said no one is more respected in and outside the building than Carr.
His dependability is unmatched. Only Los Angeles Chargers quarterback Philip Rivers, who has lined up under center for 192 straight games, has a starting streak longer than Carr's. The closest defender to Carr's streak is Detroit Lions safety Glover Quin, who is a distant second at 132 games (or nearly two full seasons behind Carr).
Does Carr think about the possible end to his mark?
"I don’t worry about it," he said. "I’ve been in the league for 11 years and every single season there has been a draft pick at cornerback. It’s always competition here. I look at it as an opportunity for me to better myself but also to teach this young guy whatever I know. I give that to him because, if the opportunity happens for him to replace me, I want him to be well-prepared so he can have the same line of success that I feel like I've had."
Carr's streak began in 2008, when he was one of six rookies to start for the rebuilding Kansas City Chiefs. A fifth-round pick out of Grand Valley State, Carr recovered a Randy Moss fumble in his first start.
Over the years with the Chiefs and Dallas Cowboys, there were some close calls for Carr. He overcame a broken hand and an Achilles injury to be able to suit up every time the defense first took the field.
"I kind of figured my body out," Carr said. "I listen to it, and it speaks to me on a daily basis."
Carr, 32, is just as committed when it comes to practices. Other than the birth of his son and the death of his mother, he has rarely missed a workout.
The Ravens typically give players 30 years and older a "veteran day off," and Carr has declined to take it. In fact, he regularly shows up early to practices. During the time when special teams practice, Carr goes through his extensive stretching routine and works on his backpedals while most other established players are still getting ready.
This workmanlike mindset has made him the most durable defender in the league. Since 2008, he has played 9,921 snaps -- or 2,397 more than any other NFL defender (Julius Peppers is second with 7,524 snaps), according to ESPN Stats & Information.
"I love the game of football," Carr said. "It's been 11 years, but when I sit down and I'm done playing this game, I'm going to look back at this and feel like it went so fast. When the opportunity presents itself, I'm going to be out there. Every single day I get up, I'm blessed to play a game and do something that I love to do. I get to wear sweatpants here every day and wear the same clothes for a whole week straight and nobody knows. I don't have to brush my teeth sometimes. I just come in and go to work."
For the NFL's No. 10 pass defense, Carr tied a career best with four interceptions and led Baltimore with 12 passes defensed.
"Brandon played very well for us," general manager Ozzie Newsome said. "And he's very, very good in our locker room."
The fiscally strapped Ravens could've created $4 million in cap space by cutting Carr, but they decided to pick up his $1.5 million roster bonus. He provided insurance in case Jimmy Smith didn't recover in time from his torn Achilles.
"Yes, he's been on the field. He's done all that, but every year is a new year, and this guy works like it's his first year," coach John Harbaugh said. "To me, that's probably why he's had the track record that he has. I feel very good when he's on the field, because he knows how to play, and he's going to give you everything he has."
The last time Carr didn't start a game was his freshman season in college. For the past 13 years, all Carr has known is lining up for the first defensive snap of the game.
Carr is realistic about his future and his streak. He's just not resigned to any outcome.
"Everything has to come to an end at some point," Carr said. "But my goal, my job, is to come out here and compete, battle for a starting job and to keep the streak alive as long as I can."