He's full of energy and ready to run, but his legs are wobbly and his direction uncertain.
"I feel ready to go, man," Harris said last week. "Got to get back in the mental department, but I'll be ready."
He had better be. Nothing, and everything, has changed for Harris in the last couple of years.
The Packers signed Harris to the practice squad on Oct. 24, 2012. Five weeks later, with the Packers slammed by injuries and Harris opening eyes on the practice field, he was promoted to the active roster.
The sample size was small but, on 34 rushes, his 4.6 yards per carry ran circles around the rest of the team's backs in 2012. Compare that figure to the per-carry averages of 4.1 for Ryan Grant, 3.6 yards for James Starks, 3.5 yards for Cedric Benson and 3.4 yards for the team's leading rusher, Alex Green. Playoffs included, Harris averaged 4.1 yards per carry. He was the offense's best player in the playoff game at San Francisco.
That from-out-of-nowhere debut was all coach Mike McCarthy needed to see. Even with a second-round pick invested in Eddie Lacy, Harris would have been the No. 1 running back entering training camp last summer. However, an injured patellar tendon sustained during organized team activities kept him on the sideline for the start of training camp.
The rest is history. Without Harris, Lacy was named the NFL's Offensive Rookie of the Year. Starks led the NFL in yards per carry and re-signed in free agency. Johnathan Franklin, a fourth-round pick last year with big-play potential, figures to return from a neck injury. Undrafted rookies Rajion Neal (Tennessee) and LaDarius Perkins (Mississippi State) had excellent careers in the rugged SEC.
So, just like when Harris was signed to the practice squad two years ago, nothing is guaranteed for him this year.
"I've been the underdog my whole life, man," Harris said. "It's nothing different to me. Shoot, it goes way back since I was a little kid. I've been an underdog my whole life. So, it's nothing I can't work from. Just back at work."
Nothing wipes the smile off of Harris' face. After all, "I could be back home sitting on the couch."
You know the story. Between stints with the Steelers and Packers in 2012, he was selling cars (or trying to, anyway). Then, during a routine physical before the team's minicamp last June, a fist-sized cyst was found pressed against Harris' lung.
"Shoot, if I would've taken a blow to the chest during a game and it would've burst, it would have been a problem," Harris said. "I dodged a bullet. That's a blessing in disguise. You never know, I could've lost my life playing this game. Yeah, I'm thankful for that (physical), so you have to take advantage of this opportunity."
"I smile at everything," Harris continued. "Even negative things, I just smile because things could be worse. I think positive every time. I'm hard on myself. I think more negative about myself than I do other things in life. I know I should be better. I'm disappointed in myself at times. Other than that, things happen for a reason. No matter what it is, no matter how much it could affect me, you've got to smile about it, because things could be worse."
Harris returned late in training camp, only to re-injure the knee during the third preseason game, and his season was over before it really started. Nonetheless, the Packers fielded their best running game in a decade. Despite Aaron Rodgers' half-season absence, the Packers finished seventh in rushing. During the eight seasons from 2005 through 2012, Green Bay ranked 20th or worse six times and never better than 14th.
"I feel like I probably could have helped out here and there," Harris said. "I felt like I let the team down. The injuries, I couldn't prevent it, but I still feel like I let the team down."
Really? Let the team down?
"That's how I feel. Just straight up," he said. "I wasn't here. I had a lot of expectations on me last year and I wasn't able to meet them. I felt like I let the team down. That's how I feel."
With the injuries behind him, Harris believes he "definitely should be" better than ever. Because of its location, the cyst obstructed his breathing, so the Packers haven't seen him with a full load of steam.
And while he's only 5-foot-7 1/4, he fits the mold of a three-down back. While Harris and Franklin are excellent pass-catching threats, Harris packs more of a pass-protection punch at a powerful 203 pounds. By contrast, Franklin is 5-foot-10 and 205 pounds.
"DuJuan Harris looks like he's back to full strength," McCarthy said after Tuesday's practice. "I would say last week I felt he knocked the rust off of a few things. But he's competing to play, just like all the other guys. I think history will show you that you never have enough good football players. History will show you here that the running back position is a very challenging position to go through the season. I see him as someone that's a part of our planning. Eddie and James did a great job last year with their opportunities and DuJuan has to fight for his opportunity."
If there's one thing about Harris, it's that he's not one to back down from a challenge. And for as good of a one-two punch as Lacy and Starks formed, there's a certain intrigue about the possibility of Harris working in a rotation with the 5-foot-11, 230-pound Lacy and the 6-foot-2, 218-pound Starks.
"We all got different styles in the backfield," Harris said. "That's great for the team. Defenses don't know what's going to hit them. I'm just excited to see how much damage we're going to do."
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Bill Huber is publisher of Packer Report magazine and PackerReport.com and has written for Packer Report since 1997. E-mail him at email@example.com, or leave him a question in Packer Report's subscribers-only Packers Pro Club forum. Find Bill on Twitter at twitter.com/PackerReport.