MINNEAPOLIS -- The Minnesota Vikings' defense is undergoing a makeover this offseason. Coach Mike Zimmer has already made several changes to his coaching staff. With free agency looming, the Vikings now face several difficult roster decisions on the defensive side of the ball.

For a team with tight finances, making moves to alleviate salary-cap concerns is its top priority, which in turn could reshape the way this unit looks in the 2020 campaign.

At the end of last season, the average age on the Vikings' defense was 26.8 years old, tied for the seventh oldest in the NFL. At one end of the spectrum are staples such as Everson Griffen, Linval Joseph, Harrison Smith and Xavier Rhodes, all of whom are either approaching or past 30 years old. That number is balanced out by younger players such as Anthony Barr (27), Eric Kendricks (27) and Mike Hughes (23).

During his season-ending news conference, Zimmer appeared to foreshadow a transformation for his defense that could be coming as soon as March.

"At the end of the day, it ends up being a young man's game, so the more that we as coaches can help develop these young guys, the quicker we can help develop them, the better it is for them," Zimmer said. "You always like to see guys have success, whether it's a young guy you've grown and he becomes a free agent and has success with some other team or it's a guy that's here you've helped develop into a good player here. All those things are important to us."

Here's a look at the areas of the defense that soon could undergo change.

Defensive line

There's good news to report. The Vikings, who were projected by ESPN's Roster Management System to be more than $10 million over the salary cap, have already started clearing space.

Griffen met two figures that voided the final three years of his contract (2020-22) by tallying six or more sacks and playing 57% or more of the snaps last season, and he exercised the right to opt out of his deal, a source told ESPN. That frees up around $13 million in cap space for Minnesota (along with roughly $800,000 in dead money).

The 32-year-old defensive end's $13.9 million cap hit for 2020 put him at risk of being cut given Minnesota's financial situation. Griffen has spent his entire 10-year career with the Vikings, and he made the decision last year to return on a restructured deal. There's a belief that Minnesota will work out a way to keep him around at a reduced price. He has proved to be a productive pass-rusher, registering eight sacks and 24 knockdowns in the regular season. And he allows the Vikings to stay put opposite Danielle Hunter -- for now -- by not having to turn to a rotation between Stephen Weatherly and Ifeadi Odenigbo at defensive end.

One area of concern is at defensive tackle. Joseph, 31, has an $11.15 million cap hit in 2020. The trade market for true nose tackles isn't as expansive as it is for other interior pass-rushers, so a Joseph trade would take some creativity. If the Vikings don't work out a restructured deal with Joseph, they would save $10.55 million against the cap if they were to release him and then turn to Jaleel Johnson, Armon Watts or a mix of the two to fill that position.

Cornerback

This is the position that could feature the most turnover on the defense. Trae Waynes and Mackensie Alexander are on the cusp of becoming free agents. Rhodes, whose struggles have been well-documented, carries an incredibly high cap hit ($12.9 million). Let's start there.

Minnesota cannot afford to bring back Rhodes at that price given what has transpired over the past two seasons. The 29-year-old cornerback allowed an 82% opponent completion rate as the nearest defender in 2019 -- the second highest in the NFL among CBs -- per NFL Next Gen Stats data. And he has dealt with myriad of injuries that have hindered his once-elite level of play. Cutting Rhodes, who is under contract through 2022, comes with $8.1 million in cap savings but $4.8 million in dead money. Restructuring his deal is possible, but a change in scenery might be best for the team and Rhodes.

That leaves the Vikings to decide whether they have the financial wherewithal to seek new deals with Waynes and/or Alexander. Financial limitations and the other corners in waiting (Hughes, Holton Hill, Kris Boyd, potentially the No. 25 pick in the draft) seem to foreshadow Minnesota keeping one or the other -- not both.

If Rhodes is gone, the Vikings might want to re-sign Waynes so they don't lose both of their starting corners. Waynes' estimated market value, according to Spotrac, is around $8.4 million per year. That's a reasonable figure given his experience and level of play. But if Waynes is shooting to get close to resetting the market, possibly putting him in the range of what Marcus Peters made on his extension with the Ravens last December, the Vikings corner could be aiming for north of $15 million per year. That's quite a large range.

For Alexander, whose season ended shy of the playoffs after sustaining a knee injury in Week 17 that required surgery, the chance to move out of the slot and test his market as an outside corner -- something several sources have indicated is a strong possibility in free agency -- might be more appealing than returning to Minnesota.

Safety

Anthony Harris is about to get paid this offseason. The question is whether it will be in Minnesota or elsewhere.

A former undrafted free agent, Harris started opposite Smith in 2019, and Harris is one of the top pending free-agent safeties. As a restricted free agent last season, Harris made $3.095 million on a one-year deal with Minnesota. His yearly salary should jump considerably given the deals already being doled out this offseason, such as the Chicago Bears' Eddie Jackson inking a four-year, $58 million extension to make him the game's highest paid safety.

The Vikings could use the franchise tag on Harris at a cost of $12.735 million. That comes with an immediate hit against the cap for a team that rarely uses any kind of tag. And it might not be in their best interest given the Vikings could argue that any player opposite a future Hall of Famer in Smith will see his level of play increase.

In his most recent mock draft, ESPN draft analyst Mel Kiper has the Vikings selecting Antoine Winfield Jr., a versatile safety who can play multiple positions in the secondary. That might foreshadow the Vikings choosing to move on from Harris and spend that money elsewhere.