Mike Zimmer has a bad defense on his résumé now, and he's hellbent on addressing that. Defensive tackle Dalvin Tomlinson was the headliner until perennial Pro Bowl cornerback Patrick Peterson signed Wednesday night, a pair of moves that instantly improve Zimmer's defense.

The NFL's quarterback carousel has captured the league's fascination this winter. Vikings observers and armchair GMs jumped into the fray by scheming trade scenarios that involved unloading Kirk Cousins and his contract. Quarterback speculation is all good fun, no matter how nonsensical some of it sounds at times.

What the Vikings need to become a playoff team again is more meat-and-potatoes. If ranking their 2020 position groups worst to best, defensive line undoubtedly belongs at the top. Offensive line comes next, though an argument can be made that their secondary was a greater or equal deficiency.

Their defensive line deserved an F letter grade last season. The offensive line gets a C-minus at best, and that's generous.

There is no mystery involved with how the Vikings improve. Defensive line, offensive line. Football 101. Exhibit A: The Super Bowl.

The best quarterback on the planet had no chance because his offensive line failed him. As uniquely talented as Patrick Mahomes is, he isn't Superman. The Buccaneers' defensive line whipped Kansas City's patchwork O-line in that game and not even Mahomes' brilliance could overcome it.

That one-sided contest reinforced the Vikings' to-do list this offseason. Without significant improvement in line play, the Vikings will be watching the playoffs at home again, which means Rick Spielman and Zimmer likely will be out of jobs.

The Wilfs have proven to be patient owners, but there must be a limit to their patience.

As the new league year begins, this is where the Vikings find themselves: They cut loose their starting left tackle and their star defensive end, Danielle Hunter, is upset about his contract with reports that he could hold out.

So, a less than ideal starting point.

The Vikings made defensive line their top priority. Two obvious explanations for that. One, Zimmer will always fight for his defense in personnel matters. And two, the line was equally atrocious stopping the run and rushing the quarterback.

That unit can be a quick fix with Hunter returning from neck injury and nose tackle Michael Pierce making his debut after opting out during the pandemic. Hunter, Pierce, Tomlinson and another pass-rushing end bring a massive upgrade in talent.

Hunter's contract situation began percolating last fall when an NFL Network reporter tweeted that the Vikings have two options: "Make Hunter the highest-paid defender in football or trade him."

That tidbit didn't just fall out of the sky. Nor has Hunter publicly disputed other reports of his unhappiness. His salary ranks far down the list of edge rushers.

The Vikings can't pretend this isn't an issue. Yes, Hunter missed the entire season because of a serious injury, but he is one of their three best players and has developed into a premier pass rusher. The team will need to re-work his contract this offseason.

In the meantime, who is their starting left tackle now that Riley Reiff is gone? Will they move right tackle Brian O'Neill to that spot? Or convert right guard Ezra Cleveland in his second season. Or hope that Reiff returns on a cheaper deal after testing the market?

Everything seems unsettled. O'Neill is a definite building block, and maybe Cleveland develops into one as well. Who else? Center Garret Bradbury remains a liability in pass protection and left guard … yeah, let's not relive that one.

Will Spielman ever get that position group fixed? He has the second wave of free agency, the draft and trade market to solidify a unit that is responsible for protecting and supporting important assets: Cousins, Cook, Justin Jefferson, Adam Thielen.

The offseason is just starting. Repairing both lines is paramount. Nothing else matters more.