NFL free agency primer: Vikings' No. 1 need is quarterback

NFL free agency begins this week, starting with the negotiating window on Monday and the opening bell for the 2018 league year at 3 p.m. Wednesday. Here's the final of a series assessing the Vikings' top five needs and how they could address them in free agency.

No. 5: Linebacker
No. 4: Tight end
No. 3: Defensive tackle
No. 2: Offensive line

These Vikings were one win from the franchise's first Super Bowl appearance in over 40 years. Now they face a blank slate at quarterback, a rarity for one of the NFL's final four teams. Head coach Mike Zimmer was candid in his uncertainty about all three internal options. Case Keenum led the Vikings to 13 wins last season, but Zimmer has lingering questions about Keenum's long-term play. The Vikings' best quarterback, Sam Bradford, has a thrice surgically-repaired left knee that is "degenerative," according to Zimmer. All while the former franchise quarterback, Teddy Bridgewater, enters free agency having not played extended game action since August 2016. Second-year passer Kyle Sloter is the only quarterback currently under contract for the Vikings.

Pending free agents: Sam Bradford (made $35 million off a two-year deal), Case Keenum ($2 million on a one-year deal), Teddy Bridgewater (coming off rookie contract).

Current roster: Kyle Sloter ($555K)

Current money invested: $555,000, 31st among NFL teams, according to OverTheCap.com.

Drew Brees (Saints) – The 39-year-old Brees has said he's "not going anywhere else," however the Saints and Brees' representatives have yet to hammer out a contract extension that will keep the future Hall of Famer away from the open market starting Monday. Brees has missed just three regular season games since 2003, meaning he'll likely become the NFL's all-time passing leader next season. He currently trails Peyton Manning by about 1,500 passing yards.

Sam Bradford (Vikings) – Bradford, 30, played one of the best games of his life when he connected on 27 of 32 throws for 346 yards and three touchdowns in the Vikings' season-opening win against the Saints. He emerged with a non-contact bone bruise in his troublesome left knee, effectively ending his season before he backed up Case Keenum in two Vikings playoff games. Can Bradford remain healthy for any NFL team?

Case Keenum (Vikings) – Keenum's breakout season came at age 29, leaving some like Zimmer wondering whether the career journeyman has made the leap to NFL starter or just caught lightning in a bottle. Keenum will likely have suitors offering him a starting job, but it's unclear if an offer will come from the Vikings.

Teddy Bridgewater (Vikings) – Bridgewater was a starting-caliber quarterback, albeit in a rigid system under Norv Turner, before dislocating and tearing multiple ligaments in his left knee. The 25-year-old Bridgewater hasn't played extended game action since the injury. He sat on the bench for eight games as Keenum's backup and will enter free agency as one of the league's most intriguing question marks at quarterback.

A.J. McCarron (Bengals) – McCarron, 27, won a grievance against the Bengals allowing him to become a free agent this week. The former Alabama cadence caller hasn't started an NFL game since the 2015 season, when he spelled Andy Dalton for three games. McCarron threw for 854 yards and six touchdowns to two interceptions and a lost fumble.