INDIANAPOLIS – NFL coaches and executives over the past week raved about the "historic" talent at running back at the scouting combine. It is a good draft if you want a tight end. The many quality edge rushers in this class impressed teams Sunday. A deep group of defensive backs figures to wow them as the event wraps up Monday.

The offensive tackles, which the Vikings desperately need? Not so much.

"I think the offensive tackle class, as good as this draft is, that's where the weakness is," NFL Network analyst Mike Mayock said. "You can find some interior guys. Once you get past the first two [tackles], there's a bunch of question marks."

And, unfortunately for the Vikings, NFL teams collectively do not allow many 300-plus-pound men with nimble feet and long limbs to reach free agency.

And, unfortunately for the Vikings, they are not the only team looking to find better blockers. A recent offseason primer from CBSSports.com listed offensive line as a top-three need for 14 of the league's other 31 teams.

The Vikings know that fixing their offensive line in one offseason isn't going to be easy.

The challenge

NFL coaches and general managers in recent years have pointed to spread offenses in the college ranks as one of the reasons why finding trustworthy linemen has become difficult. Many linemen almost exclusively line up in a two-point stance and often don't have to pass-protect as long with so many screens and quick-hitters.

"What they were able to get away with in college because they're better athletes and they don't have to be as technically sound, that shows up and takes time to develop when you get to our level," Vikings General Manager Rick Spielman said.

And because of the restrictions in practice time in the NFL's collective bargaining agreement with the players, pro coaches get less time to teach them their way to play.

The Vikings, who must solidify both offensive tackle spots, can't afford to be patient. They need somebody who can protect quarterback Sam Bradford right away. Couple that with the subpar group of tackles in this draft, and the Vikings, with plenty of salary cap space, are expected to throw cash at some of the top tackles in free agency.

The top left tackle on the open market will be Andrew Whitworth, as long as the Cincinnati Bengals don't re-sign him before 3 p.m. Thursday, when free agency officially starts after the NFL's two-day negotiation period.

He allowed pass rushers to put pressure on his quarterback only 14 times in 2016, according to Pro Football Focus. For comparison's sake, the many linemen who manned the two tackle spots for the Vikings last season collectively allowed 120 pressures.

Whitworth, a massive man at 6-7 and 335 pounds, was spotted in a hotel lobby this week wearing one of the largest pairs of khaki pants at this year's combine. He was in Indianapolis, at least officially, to sit in on competition committee meetings.

Whitworth, 35, knows Zimmer from their years together in Cincinnati.

On the left side, there is a drop-off from Whitworth. Russell Okung had some good years with Seattle, but Denver didn't bring him back after his lone season there. Other options include Kelvin Beachum, Ryan Clady and old friend Matt Kalil.

Kalil, whose rookie contract is set to expire, is healthy after undergoing season-ending hip surgery in September. The door still appears to be ajar for a possible return to the Vikings. If they do not sign Whitworth or another left tackle, a short-term deal with Kalil, who is obviously familiar with the team and the area, might make sense.

Other names

This year's top right tackles are Baltimore's Rick Wagner and Detroit's Riley Reiff, who has plenty of experience with the Lions at left tackle, too. Carolina's Mike Remmers, who spent time with the Vikings in 2013 and 2014, is also a free agent.

The free-agent options at guard this year are more promising, with Cincinnati's Kevin Zeitler, Green Bay's T.J. Lang and Carolina's Andrew Norwell among them.

But even though the Vikings last month released right guard Brandon Fusco, that position is expected to be less of a priority in free agency. They would be comfortable starting Jeremiah Sirles, who manned four positions for them in 2016, at Fusco's old spot and could add another competitor to that battle through the draft.

Mayock's top two guard prospects, Western Kentucky's Forrest Lamp and Alabama's Cam Robinson, played left tackle in college.

The first two tackle prospects in Mayock's draft rankings, and the only two he suggested he feels good about, are Wisconsin's Ryan Ramczyk and Utah's Garett Bolles. Rounding out his top six are Troy's Antonio Garcia, Florida State's Roderick Johnson, Western Michigan's Taylor Moton and Texas A&M's Jermaine Eluemunor.

"There's been an average of 10 offensive tackles going in the first three rounds," Mayock said. "I've only got about four with grades in the first three rounds."

Spielman believes "there is some depth in the class" and that the Vikings, who don't have a first-rounder but do have two picks apiece in both the third and fourth, can still possibly find a keeper up front.

"With the depth of this draft [at other positions] there's going to be some pretty good players that get pushed down our way," Spielman said last week.

But the Vikings know that only using a last-day pick on a lineman this year isn't going to cut it, which is why finding a pair of good tackles is their top offseason goal.