by Derrik Klassen

Quarterbacks are still as important as ever. A historically bad year for injuries to top quarterbacks opened the door for Case Keenum, Nick Foles, and Blake Bortles to reach conference championship games, but one anomalous season does not permanently change the league, as The Ringer's Kevin Clark expanded on earlier this week.

However, the success of the Minnesota Vikings offense, in particular, begs the question: can the quarterback be a complementary piece rather than the anchor of an NFL offense?

Case Keenum, a career backup and spot starter since entering the league in 2012, ascended into the MVP conversation after taking over for an injured Sam Bradford in Week 2. Only a year removed from a disastrous stint with the Los Angeles Rams, Keenum finished the 2017 regular season with a league-high 28.2% DVOA. He had other great stats as well, finishing ninth with 7.03 adjusted net yards per attempt and fourth with a 1.46 percent interception rate. By many statistical measures, Keenum was a superb quarterback, but the film did not always show him to be the core of Minnesota's offense.

The lifeblood of Minnesota's passing offense are the wide receivers. Adam Thielen and Stefon Diggs caught fire this season, propelling themselves to be arguably the best one-two wide receiver combo in the league. Both are former NFL draft afterthoughts -- Thielen an undrafted free agent in 2013, Diggs a fifth-rounder in 2015 -- but each has proven to be as good as any receiver in the league. When asked about the receiver duo, Arif Hasan of Zone Coverage lauded them for their ability to erase accuracy issues. "[Diggs and Thielen] win contested catches at a very high rate, and have large catch radii despite their frames -- both for low passes and high passes," Hasan told me. "They both demonstrate excellent ball tracking skills and can create extra space with physicality at the stem."

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Keenum took advantage of his afforded leniency on a deep pass to Thielen versus the Saints. After cycling through his progressions, Keenum became uneasy in the pocket, as he sometime does late in downs. Keenum felt pressure that was not necessarily there and backpedaled himself into pressure that was there. Without regaining a solid throwing base, Keenum heaved a pass up to Thielen toward the right boundary. Cornerback Marshon Lattimore committed defensive holding and defensive pass interference penalties on Thielen on their way to the ball, but that did not stop Thielen from his ultimate goal. Thielen leaped backward with Lattimore draped over him and pulled the ball in on his way down. It would be foolish to say that catch is expected of any receiver, but it is no longer shocking when Thielen makes a play like that. It has become regular for Thielen.

What is more fascinating about Thielen is how aware he is of his surroundings and how a play ought to function. Thielen can make slight adjustments in his routes or before the catch point to give Keenum a wider window to fit the ball into. Furthermore, Thielen is a quarterback's ideal scramble-drill partner. He is a perfect fit for Keenum, a former Air Raid quarterback who is fairly athletic. Scrambling and/or on-the-fly route adjustments are right in Keenum's element.

This is a play-action pass designed to look like a split-zone run. Thielen (bottom) runs a deep crosser over the middle to clear space for a back-side wheel route run by a tight end crossing tight to the formation. The idea is that the linebackers will come up to play the run and lose the tight end in the shuffle, opening up the wheel route over the top. The Tampa Bay Buccaneers and Kyle Shanahan's Atlanta Falcons offense have had success with this concept.

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As is often the case in football, the play does not go according to plan. Dennis Allen's Saints defense was prepared for the play and picked up the tight end with ease. Keenum was forced to turn back to the only other non-checkdown route available: Thielen on the deep crosser. Thielen, realizing it is late in the down and a defender is playing his outside shoulder, works back toward the line of scrimmage. Neither defender near Thielen could redirect in time, allowing Keenum to find Thielen in a comfortable pocket in between the coverage. That is heads-up wide receiver play.

Diggs is capable of the same thing. Of course, Diggs' miraculous walk-off touchdown reception is what sticks out from his performance in the division round, but the Maryland product terrorized the Saints all night long, including on a scramble drill in the end zone.

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To have mapped this play out like the last one would have been useless. In the Thielen example, the play was still fairly intact; Thielen just made an excellent adjustment to his route. This, however, is pure chaos, but Keenum and Diggs still found a way to connect. Well after his initial route had been ran, Diggs shimmied through and around defenders to create a viable window for Keenum to throw to. It was not an easy throw for Keenum to make, but not many other receivers outside of Minnesota have the savvy to get open like Diggs did.

Working with two outstanding, versatile wide receivers has made Keenum's job infinitely easier. Keenum could not ask for two pass-catchers who better suit his skill set, a sentiment Hasan cosigned when asked about Diggs and Thielen. That being said, a problem arises when teams do the obvious and double-cover one or both of Minnesota's elite receivers. It is not something defenses can get away with on every play because the offensive coordinator and quarterback can adjust, but in critical situations, it can be a crushing defensive call for an ill-equipped quarterback.

The Saints went to a Cover-0 coverage (no deep safeties) on this third-and-4 situation. Rather than blitz out of the no-deep safety look, Allen used an extra defender to cover each of Diggs and Thielen (in yellow). Keenum did not respond well to clamps being put on his best options.

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Keenum first opened the play looking to his left for Diggs. Right before the snap, the cornerback over Diggs backed off from a press alignment to a deep cushion. Keenum stuck to a rigid plan and hoped Diggs could get open anyway. When he finally accepted that Diggs was not the right option, Keenum moved back to tight end Kyle Rudolph, who ran a short hook over the middle of the field. Keenum pulled the ball up to throw to Rudolph, but was either spooked by the incoming pressure or was not comfortable with the throwing window, and he pulled the ball down to take a sack.

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In fairness to Keenum, it was a well-designed defensive call and a tough play for the quarterback to make. However, Keenum is not a quarterback to regularly dazzle with keen pre-snap foresight and post-snap sharpness. Keenum is very much a loose player, winning primarily with mobility, the willingness to force the ball to elite playmakers, and a good deal of interception luck.

As a quarterback, Keenum is plenty capable of winning the Super Bowl. Less capable quarterbacks have hoisted the Lombardi Trophy in the past, as recently as the corpse of Peyton Manning in 2015. The greater takeaway, however, is that Minnesota's offense is not reliant on Keenum being fantastic, but rather him doing enough to enable Diggs and Thielen as game-changers. When coupled with a suffocating defense, there is no denying Minnesota has found a clear avenue for success this season.

How much the Vikings' approach and success (as well as that of the Jaguars) changes the league, we do not yet know. 2017 may have simply been an oddball year, or could be the catalyst for a league-wide revolution in how to build a winning team. Regardless, the meteoric rise of Case Keenum and the Minnesota Vikings offense is a fascinating case study in how to -- at least for the moment -- win without an established franchise quarterback.