Inside the silver fencing, Miles Burris is running through bag drills under the blazing sun. He's wearing long sleeves under his black practice jersey and has on black shorts that ride up his legs every time his knees rise, revealing gray compression shorts. His No. 56 is familiarly leading a handful of Oakland Raiders linebackers, just like in 2012.

Burris was a rookie then. The 6-2, 235-pound defender was drafted in the fourth round out of San Diego State and played as a reserve his first year. But when injuries struck weak-side linebacker Aaron Curry he was called on to start 15 games. He registered 96 tackles, 1.5 sacks, and an interception. He showed potential, even though he was callow.

Once, midway through the first quarter against the Kansas City Chiefs in Week 8, he lined up to the offense's strong-side and immediately attacked downhill. He slid by the left tackle climbing to the second level and down into the C-gap, where he lowered his shoulder to take on the pulling back-side guard. This forced the running back to stretch the run before being tackled for only a one-yard gain.

A quarter later Burris was again to the strong-side when the Raiders asked him to run downfield with a tight end. It was Quarters coverage. As the tight end ran straight downfield, Burris ran diagonally to him and rolled his hips to turn downfield and stay to the inside of him while the safety covered over the top. With his first read covered, the Chiefs’ quarterback scrambled.

"It’s not a whole lot different than what he was doing in college," general manager Reggie McKenzie said to Mercury News' Tim Kawakami during the 2012 season. "Every time you looked up he was around the football, hitting something. So he’s one of those guys that will hit anything that moves.

And it’s a tribute to the coaches to kind of put him in a spot and kind of coach him up and teach him how to fit within this scheme. He’s taken to it. He had a lot of reps during the off-season because Curry went down. So he had to learn on the fly."

Despite early success, there were times when Burris' inexperience showed. His aggression sometimes turned to indiscipline, and his lack of strength and fundamentals became missed tackles. He missed 20 total, according to Pro Football Focus. A fifth came in Week 9 against the Tampa Bay Buccaneers.

One happened in the third quarter. Burris lined up at weak-side linebacker and shifted across the formation, past the center and left guard, as the play began. The running back ran in the same direction before bouncing back to the middle of the field. Burris had a clear shot at him. But when he dove forward he dropped his head and his arms slipped off the runner. He fell to the ground in frustration as the running back ran for six yards.

The growing pains were expected. Rookies never come to the NFL knowing everything. It's different than college, where it's slower and largely based on athleticism. In the NFL technique as well as health is everything.

Going into 2013 the Raiders had high hopes for Burris. Another offseason of learning the position and further familiarizing with the system was expected to prove dividends. He was also going to be starting full-time on the weak-side after the Raiders released Curry.

Then, in January of 2013, Burris had knee surgery.

The injury was undisclosed. Little would be revealed by the Raiders in the ensuing months. Still, he was expected to recover in time for offseason activities that began in May. As time passed Burris missed OTAs and minicamp, and suddenly training camp, too. Eleven weeks into the regular season, he was still gone and so was his starting job.

In Week 12, he finally came back but played only 12 snaps. It was far from the full games he played in 2012. His game, too, looked different than 2012; he wasn't fully healthy, and it showed. The next five weeks he played 30 total snaps.

“Mentally, that was one of the toughest things I’ve been through,” Burris said looking back on it. “One of the darkest years of my life, but that’s where my faith came through so greatly, and just leaning on the Lord for everything.”

Now in 2013, he's finally healthy. He's back at practice and taking part in drills while wearing a logoless silver helmet. Along with the logo, he has to earn back his starting job.