In just three years, running back Peyton Barber went from being an undrafted free agent to the unquestioned starter in the Tampa Bay Buccaneers' backfield. That arc alone has made his NFL career a success, but Barber still feels like that 2016 rookie who had to fight his way up from fifth on the depth chart. It's a mindset he adopts on purpose.

"I still consider myself to be the underdog," said Barber on the opening day of his fourth NFL training camp. "There's four or five other guys fighting for my job, and I don't plan on giving it up."

Barber got just 55 carries as a rookie when the Bucs running game mostly went through Doug Martin and Jacquizz Rodgers. He basically doubled that total in his second year, replacing Martin as the starter near the end of the 2017 campaign. Barber led the team in rushing that year, but with only 423 yards. Last year, he held the starting job from beginning to end and ended up with 234 carries and 871 yards when an expected timeshare with rookie second-rounder Ronald Jones failed to develop.

Barber's status as a potential restricted free agent this past spring plus the arrival of a new coaching staff could have endangered his spot at the top of the depth chart, but he'll start a second straight camp as the number-one option. Jones has drawn raves for his confidence and his work on the practice field so far, so that one-two punch could still develop in 2019. That said, new Head Coach Bruce Arians made a point early in the spring of saying how impressive he found Barber's game tape.

Barber never did hit restricted free agency because he signed a new deal before the league year began. He felt like his work with the Buccaneers was far from over.

"It definitely meant a lot for me to come back here," said Barber. "Like I said, I feel like I have some unfinished business here that I can definitely improve on.

"I have a lot of expectations for myself. There are a lot of things that I feel as if I didn't accomplish last year that I definitely want to accomplish this year. So, definitely a lot of expectations for myself."

Specifically, Barber mentioned getting more involved in the passing game and producing more explosive plays. That's spot-on in terms of where his statistics from his first full year as an NFL starter indicate he has room for improvement. Barber more than doubled his rushing yards last year to 871, but he averaged just 3.7 yards per carry. The Buccaneers were poor in that category as a team, even as their offense turned in some of the most explosive numbers in the NFL; Tampa Bay averaged 3.92 yards per carry last year, second-to-last in the NFL.

Barber also added just 92 yards on 20 catches despite being on the field for 616 offensive snaps. That number might not go up drastically if Jones and a third running back like Andre Ellington or Bruce Anderson is more involved this year, but he hopes it will include some more third-down exposure. Barber also expects Arians and Offensive Coordinator Byron Leftwich to call for significantly more passes to running backs than the previous offense did.

It will take work to make those improvements. Barber has already shown he's serious about putting in that work by coming into this year's camp a bit lighter than the 235 pounds at which he reported last year. Meanwhile, he and the rest of the Buccaneer running backs have had to buckle down to learn a new offense that asks more of its backs in terms of pass-protection and, as mentioned, the passing game. Barber doesn't have it fully down yet, but that's what the next month is for.

"I'd say I'm about a seven," said Barber, on a scale of 1-10 in terms of his comfort in the offense. "I'm getting there. It's definitely a lot more complicated than it was last year and the previous years."

Barber, who hails from Milton, Georgia, has found a second home and a city he loves in Tampa. He says recently bought a house in the Bay area. He clearly wants to put down roots and remain a Buccaneer for years to come. To accomplish that, he has some business he needs to take care of on the field, starting on Friday as another training camp begins.