Our Camp Countdown series continues today, with the Vikings just three days away from reporting to Mankato for training camp. To mark the team being just three days out, we'll take a look at three training camp battles to watch over the course of camp and the preseason.

1. Middle LinebackerLast year's starting middle linebacker – Jasper Brinkley – left via free agency, opening a vacancy and presenting an opportunity for someone to be the Vikings new man in the middle. Audie Cole, who played in 34 games over his first three NFL seasons, will have his eye on the prize. Eric Kendricks, selected by the Vikings in the second round of this year's draft, will also compete for the job. Working in Cole's favor is a year of experience in the defensive system, great size and proven instincts. Kendricks is an explosive athlete with great instincts himself and he also projects to be effective in coverage, which has become a necessity in today's pass-happy NFL.

2. Offensive GuardIf the offseason program is any indication, it appears there's been a changing of the guard. Brandon Fusco, who had played right guard for the first four seasons of his career, worked with the first team at left guard during the offseason. That opens up a starting job at Fusco's old spot – right guard. A pair of rookies have already spent time working with the first team in the position, with TJ Clemmings getting the bulk of the work but Tyrus Thompson also seeing some time. It's also possible that veteran Joe Berger and second-year player David Yankey could battle for the job, as well.

3. SafetyThe Vikings have one of the best safeties in the NFL in their starting lineup, but the spot next to Harrison Smith is up for grabs as the team reports to Mankato for training camp. Robert Blanton started 13 games there last season and collected 111 tackles while doing so, giving him a leg up on the competition. But the competition will be solid, with Antone Exum and Andrew Sendejo all worthy challengers and with others (rookie Anthony Harris, veteran Shaun Prater) possibly in the mix, too.

A few others to watch…

3rd Quarterback:If the Vikings are to roster a third quarterback, it will likely come down to either rookie Taylor Heinicke or veteran Mike Kafka. Heinicke hails from Old Dominion and was on the Vikings radar during the pre-draft process. Kafka has prototypical size (6-3, 230 pounds) and has four years of experience to aide him in camp.

Long Snapper:Cullen Loeffler is the longest-tenured member of the team and he heads to Mankato for his 12 Vikings training camp. He's been a solid and steadying influence on youngsters Jeff Locke and Blair Walsh, and now there's another youngster who can stand to benefit from sharing a meeting room and practice field with Loeffler. Kevin McDermott, a three-year veteran out of UCLA, was added this offseason and will compete with Loeffler for the long snapper job.

Tight End:A healthy Kyle Rudolph will give the Vikings offense an added dimension in 2015, but what the team does at the position after Rudy will be an interesting storyline to watch in camp and the preseason. Rhett Ellison is versatile and can do the dirty work, Chase Ford and rookie MyCole Pruitt seem to bring pass-catching ability to the position, and free agent signing Brandon Bostick figures to show well, too.

Punt Returner:Marcus Sherels is the incumbent starter and he's been more than solid for the Vikings in recent seasons, but there are others on the roster who could compete for reps, including WRs Stefon Diggs and Adam Thielen.

Running Back:After Adrian Peterson, the best running back in the game, and Jerick McKinnon, who had a promising rookie season a year ago, the Vikings have a ton of talent at the position. Matt Asiata has already proven himself, but Joe Banyard, DuJuan Harris and Dominique Williams will make him prove it again as they all battle for a spot in this stable.

Cornerback:Youngsters Xavier Rhodes and Trae Waynes figure to part of the plan, but what about veterans such as Captain Munnerlyn and Terence Newman? Jabari Price, a seventh-round choice last year, and Justin Coleman, an undrafted rookie this year, could also challenge to round out the bottom of this position group. Lots of talent (and competition) on this depth chart.

Backup OTs:With NFL teams only allowed to dress 46 players on game days, a versatile backup offensive tackle who can play the left or right side is a valuable commodity. Babatunde Aiyegbusi, Carter Bykowski, Mike Harris and Tyrus Thompson are just a few who will vie for a spot or two.