For Broncos linebacker Corey Nelson, being a backup is a lot harder than being a starter. It requires more discipline and focus throughout the week when practice reps are fewer and less significant.

Nelson has experienced both roles this season and his versatility to play well in each situation has earned him rave reviews from the coaching staff. He’s also a stalwart on special teams, with the second-most snaps and tackles this season.

In a defense full of stars, Nelson is one of the depth players doing dirty work and keeping the machine churning properly.

The Broncos’ third-year linebacker played well Sunday in Denver’s 20-10 win over Jacksonville, assuming a full-time role when starter Brandon Marshall left the game with a left hamstring injury in the third quarter. Marshall’s status for Sunday against Tennessee is in question, meaning Nelson may be in line for his second start of the season.

“I’ve got to step up to the plate,” said Nelson, the Broncos’ 2014 seventh-round pick. “That’s what this team is built on – the backups being just as good as the ones and filling that role.”

Nelson impressed the most with his coverage Sunday, particularly on Jaguars elusive running back T.J. Yeldon. Twice, Nelson defended Yeldon man-to-man, breaking up a pass while the Jaguars were driving for a touchdown. Coaches gave him a 90-percent grade for his performance.

Nelson competed with Todd Davis for the vacant starting linebacker spot opposite Marshall this summer. Despite losing out, he earned a role as a pass coverage linebacker and has played more than 30-percent of the defensive snaps this season. Nelson played 42 defensive snaps against Jacksonville.

Nelson, at 6-foot-1, 226 pounds, is trying to erase the perception that he’s solely a coverage linebacker. He has improved his keys in the running game and will have another opportunity against the Titans’ run-heavy offense.

“Corey can run and he’s really one of our fastest linebackers,” Broncos defensive coordinator Wade Phillips said. “We wanted to get him in the sub package because of his coverage ability, and actually, he’s played well against the run in the sub package, too. He’s made some really big hits. He’s a really good athlete just like all of our guys. If they’re good enough to play, I like to try and get them in the ball game.”

Marshall, who admitted last week that he has been having a “run of the mill” season, injured the same hamstring in October and it caused him to miss a game. Hamstring injuries typically linger and will likely be something to watch beyond this week.

Nelson’s role will be significant this week, whether Marshall plays or not, given the Broncos’ opponent. Tennessee’s top receiving weapon is tight end Delanie Walker, the AFC’s second-leading receiving tight end. Broncos defensive backs likely will shadow Walker, but Nelson also will see his share of Walker on underneath routes as well as running back DeMarco Murray.