MANKATO, Minn. — Another training camp is underway and one of the most prolific punt returners in Vikings history once again is looking over his shoulder at a potential replacement.

Nothing has been handed to Marcus Sherels since the former Gophers standout signed with the Vikings in 2010 following a tryout.

Five years later, Sherels is the franchise leader in career punt-return average (10.5 yards) and one of only three players (along with David Palmer and Mewelde Moore) to have multiple punt-return touchdowns (two).

Speedy rookie Stefon Diggs has earned praise for his route running and pass-catching abilities since the Vikings drafted him in the fifth round out of Maryland.

Diggs also is returning punts with aplomb early in camp.

“He is catching punts better than he ever has,” special-teams coordinator Mike Priefer said of Diggs. “In college you don’t have as much time to work on that stuff, so he came here with kind of a clean slate in terms of being a punt returner, kickoff returner, in terms of catching the ball.

“He’s got all the talent in the world.”

Diggs will get an extended look in that capacity during preseason games. Priefer knows exactly what he has in Sherels — a bulldog who has yet to relinquish the job.

“Every year, whether it’s playing punt corner or it’s kickoff team, whatever the case may be, every year he’s earned his job,” Priefer said. “That’s why I respect him so much, because every year he’s shown up and (been) ready to roll, and he’s earned that spot.”

Sherels, a reserve cornerback, shrugs off questions about his job security.

“It’s been a fun road,” he said. “Each and every training camp I come in and try to work as hard as I can. There’s always competition. There’s always going to be. But that’s good. It makes everyone better. It makes the team better.”

Follow Brian Murphy at twitter.com/murphPPress.