Every year offers new challenges for NFL teams. Pretty much the New England Patriots and Pittsburgh Steelers are the only teams that seem to be exempt from yearly changes.

So that means there will be some surprising low-achieving teams in 2018. Here's three AFC teams that should have less expectations heading into 2018.

Baltimore Ravens

Baltimore's defense was the second-best defense to have in fantasy football thanks to all the touchdowns it tallied during the season. The problem, though, is that despite the talent and touchdowns, Baltimore's defense still ranked outside of the top-five for top defenses in the NFL.

And the offense ranked 31st in the NFL in yards per play.

When Baltimore wasn't scoring touchdowns on defense, it wasn't putting up points. That's a major red flag when predicting future success.

You should never -- ever -- believe wins will come with a high-scoring defense. That will always even out and it requires too much luck to believe it will continue to happen in the future. Without those touchdowns on defense, Baltimore can't be trusted in 2018.

Offensively, the Ravens can't be trusted in being a better unit in 2018 either. The running game is absent and the passing game has long been a major issue. There's no vertical passing game and that won't change. Baltimore's offense was one of the worst in the NFL in 2017, so that will be a major problem in holding back Baltimore to an under .500 record in 2018.

Buffalo Bills

I'm not sure what the expectations will be for 2018 in Buffalo. But if anyone thinks this team is going back to the playoffs, they should get their health checked.

Buffalo's offense ranked 30th in yards per play. Defensively, the Bills ranked 15th in yards per play. How in the world did the Bills even make the playoffs in 2017?

One of the ways was another solid defensive effort in scoring touchdowns. And another was beating terrible teams.

Minus wins against playoff teams Kansas City and Atlanta, the Bills' other seven wins came against teams with a combined record of 31-65. You can't guarantee facing that many bad teams again, so the Bills can't be trusted. Buffalo can't pass the ball and the defense really isn't that good.

When win totals are released for the 2018 season, jump on the under for the Bills.

Tennessee Titans

They're average. That's the best way to describe Tennessee. If a few bounces went the other way, the Titans would have been under .500. Instead, they were 9-7 in 2017 and won a Wild Card playoff game against a Kansas City team that continues to see heartbreaking playoff results.

Tennessee had the 11th-ranked total defense and 18th-ranked total offense in yards per play. That's not terrible, but nothing is elite. Marcus Mariota's development looks stunted and the defense doesn't really do anything great.

The Titans are going to enter 2018 with the same boring strategy of attempting to set up the pass with a consistent rushing attack. The over/under will likely be eight wins, so expect the under to cash in 2018.

The personnel is average and capable of winning nine games (as shown in 2017). But the major negative to Tennessee is head coach Mike Mularkey. Reports indicated he was on the hot seat in the final weeks of the season only to get a likely contract extension in the offseason.

That will come back to haunt the Titans. This offense is going nowhere and there's nothing special on the defensive side of the ball. Book the under in 2018.

Upon further reflection...

OK, so the Titans did something nobody was expecting and actually parted ways with Mularkey. That changes things. 

I'll give Tennessee credit. They didn't just look at that one playoff win and automatically give Mularkey an extension. That takes guts, but the results on the field and the growth of this team made it necessary to look elsewhere. 

So, don't book the under for the Titans just yet. They may have some life after all. But if you're looking for another team with diminished expectations...

Jacksonville Jaguars

This seems silly, too, especially with the Jaguars currently one step away from the Super Bowl. 

This goes along the same lines from what I was witnessing in Tennessee. There's one major problem with this team and it's unlikely to go away in 2018 thanks to this playoff run. 

Blake Bortles is not the answer at the quarterback position. The Jaguars won games in spite of Bortles for the most part in 2017, but thanks to a deep playoff run this year, it's more than likely he'll be the starting quarterback again next season. 

Jacksonville does an elite defense, but in the NFL, that only buys you so many wins in the regular season. Eventually you need to move the football at a consistent rate, and I'm just not seeing that with the Jaguars. 

Most teams are set at eight wins in win totals, but I would anticipate the Jaguars may be at 8.5 or even 9 when those are released in the summer. The safe pick is to go under those numbers. 

Scott Levine is the Associate Editor for the Clinton Herald. During his free time, he blogs about fantasy sports and handicaps games. Check out more at Against The Chalk. 

Scott Levine can be reached at scottlevine@clintonherald.com or on Twitter @ScottLevineCH