NFL free agents can officially start signing with teams this afternoon. The Vikings have already addressed two major needs -- albeit with players who were already on the field during a 5-10-1 season for them a year ago -- by locking up QB Matt Cassel and DE Everson Griffen. Now the question is: How many moves are left?

The Vikings reportedly will still have about $25 million in cap space after the Cassel and Griffen deals are on the books. Some of that needs to be set aside for draft picks. The rest will be a test of the Vikings' priorities and patience.

Here's what we know: It's becoming increasingly harder to win in the NFL without good play in the secondary. The Vikings have two defensive ends who are young, hungry and can sack the quarterback. But they finished in the upper half of the NFL (tied for 13th with 41 sacks) in 2013, and their defense was still dismal.

They must, must, must target a high-level cornerback in free agency. It's the one big-splash move that makes sense in terms of the money they have to spend and their most pressing need. Alterraun Verner is the name most often brought up. He could fetch $10 million a year as a 25-year-old corner with a strong track record in Tennessee. He played all 16 games in each of his four seasons. He had five interceptions last year as well as 22 total passes defended. Put him with Xavier Rhodes. Get full seasons from both. Add more depth in the draft. It doesn't solve all the world's problems, but it's a great start.

We can live with modest, patient approaches at other positions. Find a plugger at nose tackle. Find reclamation project and a late-round pick who can compete for spots at guard. Draft a playmaking linebacker early. But go get that playmaking corner and don't be afraid to splurge.