"I have to keep playing hard if I want to be here," said Demps, 22, who leads the Ravens in total turnovers this preseason, including all practice sessions. "I always want to be a better player and a better person. I want to be perfect, even though I know that's not possible.
"I can't worry about anything I can't control. I always have to be ready to play football."
Entering the preseason finale on Thursday against the New York Giants, the former walk-on from San Diego State appears to have the inside track to take the job of Mitchell, a veteran special teams standout, in the first defensive huddle.
Even if this competition isn't quite over yet, with Mitchell and sixth-round pick Chad Williams not going anywhere, Demps has certainly built a strong case for defensive coordinator Mike Nolan to consider.
"I've got to get that fire back," Mitchell said of the challenge from Demps. "I took things for granted that I was going to start. I came in overconfident. Will's playing really well right now, but I'm not giving up."
Beyond his bid to join the Ravens' starting defense, Demps also has a new story to tell his friends: about the time he sacked All-Pro quarterback Donovan McNabb.
Starting for the first time in Friday night's 13-12 victory over the Eagles, Demps wrapped up the imposing, acrobatic McNabb in the open field to stop Philadelphia from converting a 3rd-and-9 on the Ravens' 18-yard line.
When Demps made that tackle on the Eagles' opening drive, he stood up and looked around as if he wanted to tackle someone else. Middle linebacker Ray Lewis acknowledged the rookie's accomplishment with a fierce hit of his own.
"It sank in later," Demps said. "It was exciting. After the game, a couple of my friends called and said that I tackled Donovan McNabb."
During the Ravens' 12-6 victory over the Detroit Lions in the preseason opener at Ravens Stadium, Demps captured immediate attention by winning the game by returning a Joey Harrington interception for a touchdown late in the fourth quarter.
In a 34-16 loss to the New York Jets, Demps collected the lone Baltimore interception.
"The key for him is, ‘How much can he absorb?'" Ravens coach Brian Billick said of Demps. "Physically, there's no question he can play. The safeties, to a large degree, have to get us in and out of certain things. They have to see combinations.
"They have to be very communicative. For a young man, that's the toughest thing."
Billick reiterated in each of the past two days that he's not concerned with who begins the game on defense or who inherits which roles. He said the Ravens have yet to establish their final starting rotation, and he noted Mitchell's play as being solid. Mitchell collected five tackles against the Eagles.
Mitchell, 27, has greater stature at 6-foot-1, 211 pounds than Demps, who is generously listed at 5-11, 210 on the roster.
Mitchell was promoted before minicamps began when last year's starter, Corey Harris, signed an offer sheet with the Detroit Lions this off-season.
"It's definitely going to be a group effort," Billick said of the two safety positions, where first-round pick Ed Reed will likely succeed departed All-Pro Rod Woodson at one spot with Demps, Mitchell and Williams competing for the job opposite him.
In the NFL, players rarely care about draft status once someone has proven they can be relied upon. So far, Demps has helped his cause enough that even an established starter like cornerback Chris McAlister is nodding his head in approval.
"Demps is definitely capable," McAlister said. "He has made plays every preseason game. He has shown he can adapt to being out there in the line of fire."
Forgive Demps if he doesn't pinch himself to see if he's in the middle of an NFL dream.
He had to climb his way up the Aztecs' depth chart after arriving on campus from Palmdale, Calif., sans an athletic scholarship. He left San Diego State with two all-conference selections, 229 career tackles, nine pass deflections and five interceptions.
For Demps, this feels like his freshman year all over again, only on a much higher plane of football.
"It's similar," Demps said. "It's kind of the challenge of the athlete. Who knows if I would have been signed out of high school if I would have done as well as I did? You've got to push yourself harder than the guy who was drafted.
"I can't worry about being overlooked. I just have fun playing football because that's what I love to do."