Still, you can't wipe the smile off his face.
"Against Miami, (defensive line) Coach (Don Johnson) was like, 'Your hands and feet are wrong,' but it was like, 'Yes, I'm out here.' Midway through the third quarter I looked up at the sky and said, 'Thank you, Jesus, for letting me get back out here. This is what I love to do.' "Just getting out on the football field again -- in a game -- was like being born again."
Campbell, a Thornwood product and Bears free agent, had his world turned upside down in March 2004. Less than a month before the NFL draft, the Notre Dame defensive tackle was doing an individual workout for the Baltimore Ravens in South Bend and partially tore the anterior cruciate ligament in his left knee. Considered by most as a first-day draft pick -- going in the first three rounds -- Campbell was left out in the cold. He was rated the No. 20 defensive tackle by The Sporting News entering the draft, No. 14 by Pro Football Weekly and No. 13 by ESPN.com's Len Pasquarelli.
"This (injury) may drop him out of the draft entirely," Pasquarelli said then. "This is a big, fat red flag next to his name."
Pasquarelli was right. Campbell went from everybody's buddy to a guy wondering who his real friends were.
"Before the injury everybody was tugging on me. Then everybody kind of fell off," Campbell said. "You find out who your true friends are, people that are more than just associates and people who have more than a monetary interest in mind.
"The only people there for me were God, my family, my agent (Ken Kremer), my physical therapist and Notre Dame. Having Notre Dame was big because when I was on my couch, unable to walk, I had a few job offers on the table. That was because of Notre Dame alumni."
Campbell remembers watching the draft tracker on ESPN and feeling "worthless" seeing all those names go by and never seeing his. He started 34 of 44 games for Notre Dame, totaling 87 tackles and 11 sacks, which would have earned him a guaranteed contract and big money, but ultimately went undrafted because he was considered damaged goods. Most teams don't waste draft picks on injured players, especially one who was going to be spending a year away from football rehabilitating.
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Campbell knew there were no guarantees, but he had his faith in God and his family by his side. His hometown team, the Bears, gave him a small signing bonus and an opportunity. That's all he ever wanted. Now Campbell is focused on not letting them down.
"One thing (Bears general manager) Jerry Angelo told me when I was hobbling around on crutches -- and he's a realist -- is he said we're deep on the defensive line," Campbell said. "But he said that's why we're rehabbing you on our dime and that's why we're taking a chance on you.
"When an organization does that, you're either special or you're perpetrating. I don't want to be the latter part. I want to be the guy that makes it. You hear the comeback stories about guys coming back healthy, but they don't make it. I want to be that story of the guy who makes it.
"The Bears took a chance on me and I don't want to let them down. I'm a hometown kid, I love the Bears. I've established friendships and relationships and I really want to be a part of this. I think (this defense) can be special."
Campbell has grown close to his defensive linemates, especially Tommie Harris, a former first-round pick in 2004 -- the same year Campbell was supposed to be drafted.
"Darrell has a tremendous motor," Harris said. "You watch him play and you see a guy who plays like he's been given a second chance. It was almost gone, but he's back healthy and doing all the right things. We need him; he belongs here.
"It's one of those things that happened by chance. It's life, but he played his cards right. When his knee went out, he stayed positive and worked even harder."
Defensive line is the deepest and strongest area on the Bears, another obstacle for Campbell in his quest for a spot on the 53-man roster.
Already locked into spots at tackle are Harris, Tank Johnson, Alfonso Boone and Ian Scott. Add in defensive ends Adewale Ogunleye, Alex Brown, Michael Haynes, and Israel Idonije the numbers don't look good for Campbell.
"It's going to be a process with him because of his inexperience," Bears defensive coordinator Ron Rivera said. "But what we really like about him is he's an explosive guy."
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Campbell was raised by his mother, Jeannette McGee, after his father walked out on them when he was 3 years old. Jeannette worked long hours at People's Energy in Chicago and raised her son on her own.
"I've always been a hard worker and I get that from my mom," Campbell said. "She never would take off of work. She's a field worker, doing a man's job, but she's a strong black woman. I can appreciate that and it inspires me to work harder because she's gone through a lot of different things."
When Darrell was 12, a father figure finally entered his life. Milton McGee, whom Darrell calls his "father," eventually married his mother on Sept. 3, 1995. Milton is a regular at Bears training camp. Campbell said it's like Milton is in the huddle with him.
"My mom has been real positive and my dad has been so instrumental," Campbell said. "He's like a ninja -- he's popping up everywhere. He's always scoping me out and keeping an eye on me. I always try to be on my best behavior because of him."
Campbell underwent surgery to repair his knee in April 2004 -- four days before the draft -- at Rush Presbyterian-St. Luke's Medical Center in Chicago. The best-case scenario for recovery was three to four months, but the 6-foot-4, 290-pound Campbell spent six months rehabilitating. He said he got back on the field after six months and knew he wasn't ready.
But just getting back out there was a miracle in itself.
"I had to reset everything and go back to the basics," Campbell said. "You have to crawl before you walk, walk before you run, and (the knee) was all new to me."
Making the practice squad was worst-case scenario for Campbell. Making the Bears roster is obviously his dream, but for all Campbell has been through the last year and half, he'll do anything to keep playing the game.
"It's just nice being out here and doing what you love to do," said Campbell, who has his degree from Notre Dame. "Any occupation, you can't ask for anymore than that. I definitely understand it's a business.
"I still have to get some things figured out, but I feel I've had a pretty good camp and I've heard good things from the press and my peers. When the vets notice, you must be doing something right. All I wanted was a chance and I'm getting that."