With NFL free agency now in its third wave, which is probably more like a ripple, the Vikings are done making significant additions, having signed a pair of free-agent linemen and potentially a starting safety.

Bringing back veteran outside linebacker Chad Greenway, which they are still expected to do, would be significant in terms of his value in the locker room and his meaning to the community, but not so much financially.

The next big deal they get done will presumably be with Pro Bowl safety Harrison Smith, though recent history suggests it may take a while.

The Vikings under general manager Rick Spielman, with a big assist from salary cap guru Rob Brzezinski, have put an emphasis on signing ascending young players to extensions before the final year of their rookie contracts. But talks typically haven't heated up until training camp.

Tight end Kyle Rudolph, in 2014, and kicker Blair Walsh, last season, got their lucrative new deals shortly after the Vikings reported to Mankato. Slot receiver Jarius Wright was extended last summer after the Vikings had moved back up to Winter Park to wrap up training camp. Starting guard Brandon Fusco signed his deal a day before the 2014 season opener.

The Vikings at some point this offseason will explore a new deal with Smith, one that will surely place him among the NFL's highest-paid safeties.

They have $11.2 million in salary cap space, according to NFLPA figures, though they will need a chunk of that to sign Greenway and their draft picks and will also keep a cushion in case they need to sign somebody during the season. But they made sure to leave enough cap space to fit Smith's deal.

So how big of a contract extension might we be talking about here?

I reached out to an NFL agent who does not represent any Vikings but is familiar with how they do business. He speculated that Smith could garner a five-year, $45 million extension with about $25 million guaranteed.

That deal would basically be tacking on four years and roughly $40 million to the $5.3 million he is already getting in 2016 on his fifth-year option, which the Vikings exercised last spring on the 2012 first-round pick.

That deal, with an average of $9 million per year, would make Smith one of the top five highest-paid safeties in the league, not including Eric Berry, the Chiefs safety who will make $10.8 million via a franchise tag in 2016.

Earl Thomas, who is widely regarded as the NFL's top safety, is currently on a four-year, $40 million deal with the Seahawks. Devin McCourty re-signed with the Patriots on a five-year, $47.5 million deal last offseason.

Given how salaries have inflated this offseason after the salary cap spiked, Smith will probably want to be paid at least similarly. And given his impact on this defense, his agent, Brian Murphy, can make a compelling case.

Maybe that's why Spielman playfully said in February that he wanted us to describe Smith as one of the NFL's "better" playmakers in our stories.

"Better. Please put better. Not best. Better playmakers at safety," Spielman said with a smirk. "He can play free and strong. He can be effective on the deep end, and he's just as effective when he gets walked up to the line of scrimmage. So he's a good safety. Good. I'm just saying he's a good safety."

If for some reason the Vikings and Team Smith are unable to find common ground, the Vikings do have the ability to tag Smith next offseason and keep him under team control for 2017 at a projected fee of $11-12 million.

But their recent track record suggests that they will get something done, probably after the Vikings report to Mankato but perhaps sooner.