MINNEAPOLIS -- Since free agency began on March 11, the Minnesota Vikings have been busily working the free-agent market to upgrade their defense. Those efforts, according to ESPN Stats & Information, have landed the Vikings among the league leaders in guaranteed money spent since the start of the new league year.

The Vikings have given out $50.2 million in guaranteed money since March 11, which is the fifth-most in the NFL. Only the Buccaneers ($74.3 million), Broncos ($65.5 million), Browns ($63.8 million) and Raiders ($51.0 million) have included more guaranteed dollars in new contracts.

That sum is the cost of doing business for a team that ranked second-to-last in the league in defense last season, but even though the Vikings have spent a sizable amount of money to sign players from other teams, the number itself shouldn't necessarily signal a departure from the draft-and-develop philosophy the team has employed the past three years, largely because of how much of the guaranteed money was wrapped up in the Vikings' new deal for 2010 fourth-rounder Everson Griffen.

Griffen got $19.8 million guaranteed as part of his five-year, $42.5 million contract, and he'll have been paid all of that money by the end of next season. The only money that would accelerate onto the Vikings' salary cap if they cut Griffen after 2015 is the $3.6 million in signing bonus proration left on his deal. The deal that includes the second-most guaranteed money -- for defensive tackle Linval Joseph -- has a similar structure. In that case, the Vikings gave Joseph $7.1 million in base salary guarantees, and a $2.4 million roster bonus they paid him last month, so the only cap charge they'd face by cutting him after 2015 is the $1.8 million of bonus proration left on his deal.

In total, the deals the Vikings gave out this spring would only include $5.73 million of dead money after the 2015 season. The pay-as-you-go method employed by assistant general manager Rob Brzezinski has allowed the Vikings to give out big contracts and stay out of salary cap trouble. Even the $45 million deal the team gave wide receiver Greg Jennings a year ago will only carry a $6 million cap charge after this season; the Vikings gave Jennings $17.8 million in guaranteed money, in the form of a $10-million signing bonus and guaranteed base salaries in each of his first two seasons. That deal came with a bigger signing bonus than most of the contracts the Vikings have done lately, but on a $45 million total deal, the Vikings' cap burden in the final years of Jennings' contract is still relatively small.

That structure will also allow the Vikings to be aggressive next year, should they choose to do so; with the cap possibly rising as high as $140 million, the Vikings could already have $30 million in cap space for 2015, before restructuring any deals or releasing any players.