Oregon’s unique brand of up-tempo football accomplished more than winning some games over the last half-decade. The Ducks revolutionized the sport, helping to usher in a new era of fast-paced, entertaining offenses.

Three straight conference titles won from 2009-11 changed the complexion of the Pac-12. Arizona, Arizona State, Cal and Washington State all hired head coaches dedicated to an explosive style of no-huddle football in an effort to catch the Ducks.

With four league crowns and two national title game appearances in the last seven seasons, Oregon remains the Pac-12 standard bearer.

Some cracks have shown in Oregon’s foundation recently, however. Last year’s 9-4 finish tied the program’s worst since 2007, and marked the Ducks’ first single-digit-win campaign since Mike Bellotti’s exit as head coach.

A monumental collapse in January’s Alamo Bowl – the Ducks squandered a 31-0 halftime lead to lose, 47-41 in triple overtime – sends Oregon into a soul-searching spring.

5 Storylines to Watch During Oregon Spring Football

1. Dakota Prukop to the Rescue?

Replacing 2014 Heisman Trophy winner and three-year starting quarterback Marcus Mariota was never going to be easy, but Eastern Washington transfer Vernon Adams did so admirably – when he was healthy.

A broken finger limited Adams for an early stretch, and an injury sustained in the Alamo Bowl was the prelude to the Ducks’ implosion.

Adams graduated, opening another springtime quarterback competition. Head coach Mark Helfrich could again turn to an FCS transfer to captain the offense, this time Montana State import Dakota Prukop. Prukop flourished under Chip Kelly disciple Tim Cramsey at Montana State, running a system with striking resemblance to that which Oregon runs.

Oregon’s losses in 2015 tied directly to quarterback play. If Prukop proves to be or at least nearly as effective as Adams, the Ducks will return to the Pac-12 championship race. Otherwise, Oregon can anticipate more pronounced struggles in 2016.

Related: College Football's Top 20 Quarterbacks on the Rise for 2016

2. Secondary Improvement

The secondary had long been the strength of an underrated Oregon defense. Last season, the back end was a decided weakness, as the Ducks ranked an abysmal No. 126 nationally against the pass.

Playmakers Tyree Robinson and Charles Nelson (who could move back to offense) return, giving this year’s secondary more of a veteran look, but inexperience up front will test the Duck defensive backs’ savvy early.

3. A DeForest-less Defensive Line

Having an All-American like DeForest Buckner up front masks deficiencies. Given the Ducks’ defensive woes in 2015 it’s scary to think how bad things would have been without Buckner making as many plays as he did.

Last season, Buckner accrued 17 tackles for a loss and 10.5 sacks – monster numbers in any situation, but especially so considering double-teams Buckner often faced from opposing blocking schemes.

Buckner impacted Oregon’s run and pass defense alike, stuffing rushing lanes for ball carriers, and bearing down with relentless pressure on quarterbacks. A restructured defense under new coordinator Brady Hoke won’t get any one player capable of filling Buckner’s void. Oregon must find multiple playmakers to compensate for the missing production.

4. Brady Hoke’s Defensive Philosophy

Helfrich overhauled his coaching staff in the offseason, something of a departure from Oregon convention. Longtime assistants have often filled prominent roles at Oregon, including former defensive coordinator Don Pellum.

Bringing aboard former Michigan head coach Brady Hoke really deviated from the norm. But given the last time an Oregon head coach reached well out of his comfort zone when tabbing a coordinator, it brought Chip Kelly’s offense to Eugene.

Expecting Hoke to have a Kelly-like, transformative impact on the defense might be setting the bar too high. However, his promise of a more aggressive approach, per Ryan Thorburn of The Register-Guard, has to be encouraging after two seasons of lackluster turnover production.

5. Rolling with Royce

There are questions abound for Oregon heading into the 2016 season, but running back isn’t one of them. The only question pertaining to a unit headlined by junior Royce Freeman is if the talented power-back has the juice to bring another Heisman back to Eugene?

Freeman put up remarkable, yet somehow overlooked numbers in 2015: 1,836 yards on 283 carries for 17 touchdowns.

Freeman’s a prime candidate for the illustrious 2,000-yard club, which typically means candidacy for the Heisman Trophy. He’ll need consistent play from his quarterback to draw away defensive attention – his lowest production games last season were against Michigan State and Utah, with Adams either playing through or sidelined with a broken finger.

Pre-Spring Oregon Outlook in the Pac-12

Stanford winning its third Pac-12 championship in the last four years might indicate a shift of power in the Pac-12 – but that’s only if you fail to account for the Cardinal being held out of the College Football Playoff last season by a home loss to Oregon.

The 2015 campaign brought failure at a level not experienced in Oregon for some time. And yet, the Ducks’ “bad” year would be celebrated as a rousing success

The Ducks face unquestionable challenges entering Mark Helfrich’s fourth year as head coach. The instability at quarterback in a post-Mariota age is disconcerting, and the regression of the defense presents challenges in the offensive-friendly Pac-12.

— Written by Kyle Kensing, who is part of the Athlon Contributor Network and a sportswriter in Southern California. Kensing is publisher of CFBHuddle.com. Follow him on Twitter @kensing45.