Vikings training camp snapshot: Offensive line

Aaaaand …. here we go! In many ways, the Vikings' 2013 season officially gets underway Friday – first training camp walkthrough at 10:30 a.m., first practice at 2:45 in Mankato. And yes we know a lot can and will happen between now and Sept. 8, the day the Vikings open the regular season at Detroit. But taking the 90 players currently on the roster, we're delivering our in-depth position-by-position report as a primer for the opening of camp.

OFFENSIVE LINE

Currently on roster: 15

Likely to make opening day roster: 9

Certain to make the team: Matt Kalil, John Sullivan, Phil Loadholt, Brandon Fusco, Charlie Johnson

On the bubble: Jeff Baca, Travis Bond, Joe Berger, Seth Olsen, Troy Kropog, Kevin Murphy, Brandon Keith

Practice squad candidates: Tyler Holmes

Biggest offseason developments: The Vikings needed to dig deeper into the vault than they had hoped to but made it a major priority to re-sign right tackle Phil Loadholt, finalizing a four-year, $25 extension in the final hour before Loadholt would have hit the open market as a free agent. … Sullivan underwent microfracture surgery on his right knee and subsequently was held out of Organized Team Activities and mini-camp.

What we'll be watching: The Vikings have said all along that they expect Sullivan to be ready for training camp, that the surgery he had on his knee shouldn't be a long-term deterrent. But we still need a little convincing that the top-notch center is ready to return to form. We'll be watching Sullivan's mobility in the early stages of camp just to make certain he's back at full strength. Berger took nearly all of the first-team reps at center in Sullivan's place through the offseason program and would be the first option there if a setback were to occur.

What must also be kept in mind is that the Vikings' first training camp practice comes 44 days before their first regular season game. Having Sullivan at full tilt for the latter will be far more important than pushing him in the early days of camp.

Star Tribune offseason excerpt:

With the previous three-and-a-half days giving Loadholt's agent an opportunity to measure other teams' interest and determine a true market value, Loadholt held great leverage throughout a process that was still, in his words, stressful.

He will be due to make $2.9 million in base salary in 2013 and could earn as much as $4.75 million.

Just as gratifying, Loadholt said, was the opportunity to remain a Viking, to continue plowing holes for league-MVP Adrian Peterson, to remain a part of a starting quintet up front that has seen its chemistry grow.

Loadholt said he never feared a possible departure. But he also never exhaled to feel like he would remain here for certain.

"Like I said, the business part of football is very shaky," he said. "So it was definitely a tough time for myself and my family. You never know what can happen. So there was definitely times I was a little nervous."