With the Buffalo Bills nowadays, change is the only constant. Over the past 19 years, they've had seven different full-time head coaches, none of whom has lasted more than four years.

No pressure, Sean McDermott.

McDermott is set to become the team's newest head man after the dismissal of Rex Ryan prior to Week 17. McDermott is another defensive mind, having spent his past six years as the defensive coordinator of the Carolina Panthers. And when you see what happened to the Bills this past year, it'll become a bit more clear why this focus on defense was almost a necessity.

McDermott -- if past history is any indication -- won't have a long leash with a team so accustomed to turnover. Does he have the pieces to turn this team around and hold a job longer than a single rookie contract? The answer here could absolutely be "yes," but there are just a few factors that will go a long way in determining this.

Let's take a deeper look into the Bills to see what type of team McDermott is inheriting. Most of this will be done using numberFire's Net Expected Points (NEP), the metric we use to track the efficiency of both teams and players with all team totals being adjusted for strength of opponent.

Here's how NEP works. Prior to each play, there's an expected number of points for the offense to score on its current drive. A three-yard completion on 3rd and 2 picks up a first down, resulting in an increase in those expected points. That same three-yard completion on 3rd and 4, however, likely results in a punt, and NEP helps quantify the difference between those two outcomes.

McDermott has plenty of solid assets at his disposal in Buffalo, but there are also some critical questions that need to be answered. Let's go through those now to see what lies ahead in Year 1.

Settling on a Quarterback

Any discussion around the Bills right now must start and end with what they plan to do at quarterback. Tyrod Taylor has held down the fort the past two years, but the team may cut him loose. Doing so would not be starting McDermott's tenure on the right foot.

As numberFire's Dan Pizzuta wrote back in December, Taylor isn't the Bills' biggest problem. Even though Taylor had suffered from a dip in production from his first year as the starter, he still pumped out numbers that made him appear worthy of starting in the NFL.

For the 2016 season, Taylor finished 19th in Passing NEP per drop back of the 39 quarterbacks with at least 100 drop backs. This put him just a few spots behind Andrew Luck and Russell Wilson while finishing ahead of Philip Rivers, Carson Palmer, and Eli Manning. Taylor wasn't elite by any means, but he was certainly serviceable.

It would be fair to be skeptical of Taylor's marks if they were simply from one year. That's not the case, though, as these were a continuation of what Taylor did last year. Then, he finished 10th in Passing NEP per drop back, one slot behind Matt Ryan and two behind the eventual MVP, Cam Newton. We have now 897 drop backs from which to judge Taylor with the Bills, and the returns have all been fine. Why not build around that?

The other factor to consider here is that all of Taylor's Passing NEP numbers will include expected points lost on sacks, and pass protection was certainly not an area of strength. The Bills finished 28th in the number of expected points lost on sacks on a per-drop back basis. If we take sacks out of the equation, Taylor averaged 0.27 Passing NEP per attempt this year, the 13th-best mark in the league, tying him with the widely-celebrated Derek Carr.

Certainly, the quarterback plays a role in sack totals, but this wasn't all on Taylor. The Bills ranked 31st in Adjusted Sack Rate, according to Football Outsiders, a metric that adjusts for down, distance, and opponent. The team did not provide Taylor any help up front, and yet he still excelled.

Finally, Taylor did all of this despite wide-spread injuries to the receiving core. Sammy Watkins missed eight of the 15 games in which Taylor played, Robert Woods missed three, and tight end Charles Clay missed one. These were his top assets, and they all missed time. That should at least help explain part of Taylor's dip in production from last year.

When you add in that the Bills were second in Adjusted Rushing NEP per play, this really isn't a terrible offense. Assuming they retain Taylor, that is. If not, they'll be forced to turn elsewhere at the position, and that could put McDermott in a rough spot if he needs to win right away.

Major Defensive Deficiencies

The offense -- again, assuming Taylor returns -- really isn't bad for the Bills. The defense, however, is a different story, and it helps explain why the Bills turned to another defensive mind.

Overall, the Bills finished the season ranked 20th in Adjusted Defensive NEP per play. They were also 20th against both the rush and the pass, meaning this place was just brimming with mediocrity. That would be bad enough as is, but it got progressively worse as the season went along.

Through the first nine weeks, the Bills ranked 18th defensively. From then on, they fell all the way to 26th overall, including a 30th-place ranking against the rush. That's not going to get the job done when the goal is breaking a 17-year playoff drought.

Although part of this is due to gaps in personnel, McDermott's Panthers did perform well in these areas. Despite playing with an inexperienced secondary and missing star linebacker Luke Kuechly for six games, the Panthers were ninth overall defensively, eighth against the pass, and 13th against the rush. It may not be immediate, but McDermott has proven that he can assemble a solid defense when he has worthy components.

A major aspect of the Panthers' competency against the pass in 2016 was an ability to get pressure on the quarterback. Panthers opponents lost the second-most NEP on sacks on a per-drop back basis in the entire league, falling behind only the Arizona Cardinals. The Bills weren't terrible in this department with a 13th-place finish, but growth here could help the team make up ground defensively in a hurry.

Conclusions

In coming to the Bills, McDermott has some mighty interesting pieces that could help him excel from the jump. Those pieces don't come without their questions, though.

The first order of business in Buffalo should be appeasing Taylor and making him the team's starting quarterback. He showed this year that he can do well even when surrounded by a multitude of wide-receiver injuries and issues on the offensive line, legitimizing the efficiency he showed in 2015. If quarterback isn't currently an area of weakness, they shouldn't make it one by cutting ties with Taylor.

Once that's settled, the defense immediately becomes the focal point. Ryan failed to fix things there in his two years, necessitating the hiring of someone with McDermott's expertise. That said, if he can bring elements of the Panthers' defenses from the past two years -- specifically, the pass rush -- McDermott could also right this ship in short order.

McDermott has the tools he needs to succeed in Buffalo before the offseason work even begins. That's most of the battle. Now, it's just a waiting game to see if he can finally get the team over the hump and back into the playoffs or if he'll wind up back on the scrap heap like so many to coach this team before him.