Free agency unofficially started at 11 a.m. CT when the NFL's two-day negotiating period begins. Free agents can’t actually sign with new teams until the new league year starts on Wednesday at 3 p.m. CT. But this year, during the “legal tampering period,” teams and players can negotiate all aspects of a contract. They just can’t put pen to paper until Wednesday.

That, of course, doesn't apply to re-signing pending free agents. The Vikings have already gotten deals done with safety Andrew Sendejo and backup nose tackle Kenrick Ellis. They have also had discussions with the agents for guard Mike Harris and others. But once the clock struck 11 a.m., those players were free to talk to other teams. They can't go on visits yet.

The Vikings, as usual, will focus on retaining their own priority free agents. But general manager Rick Spielman said last month that the Vikings could "dabble" there if the right player comes along at the right price.

The team's biggest needs are offensive linemen, wide receiver and safety.

It looks like there will be a number of proven veteran linemen available on the open market, including Seahawks left tackle Russell Okung, Bengals right tackle Andre Smith, Ravens guard and tackle Kelechi Osemele and Browns center Alex Mack and right tackle Mitchell Schwartz.

The Bears tagged wide receiver Alshon Jeffery, so that potential top target won't reach free agency. Second-tier options at the receiver position include Mohamed Sanu and Marvin Jones of the Bengals, Rueben Randle of the Giants, Anquan Boldin of the 49ers and Travis Benjamin of the Browns.

A pair of Bengals are among the top free-agent safeties: George Iloka and Reggie Nelson. Other options include Eric Weddle of the Chargers, Tashaun Gipson of the Browns and Rodney McLeod of the Rams.

The Vikings have about $23 million in salary cap space right now, according to OverTheCap.com. That figure does not include the deals for Sendejo and Ellis, which have not been filed to the league yet. The Vikings can create more cap space if needed by releasing highly-priced veterans such as wide receiver Mike Wallace and offensive tackles Matt Kalil and Phil Loadholt.

There is no deadline for the Vikings to make a decision on Wallace. If they want to move on from Kalil, they must cut him by Wednesday or his $11.1 million salary for 2016 will become fully guaranteed. Loadholt, meanwhile, has a $550,000 roster bonus due on Friday.

So buckle in, Vikings fans. This figures to be a busy week one way or another. And we will be keeping tracking of all the moves right here.