It's early in the 2019 NFL season, but we've already seen various trends develop. For several of last year's rookie standouts, these trends aren't exactly encouraging.

From Baker Mayfield's sudden lack of pocket poise to Josh Allen's lingering turnover problem, some notable second-year players are showing signs of the dreaded sophomore slump. The question is, which of these issues are a legitimate cause for concern?

That's what we'll examine here, as we dig through those problem areas facing the top second-year players in 2019.

Sony Michel, RB, New England Patriots

Running back Sony Michel was a bona fide weapon for the New England Patriots last season. A physical between-the-tackles runner, he battered opposing defenses to the tune of 931 rushing yards and 4.5 yards per carry as a rookie in just 13 games.

However, Michel hasn't been the same dominant runner this season. He came into Week 6 averaging just 3.4 yards per carry, often conceding touches to the likes of James White, Rex Burkhead and Brandon Bolden.

This is an issue because Michel doesn't offer a lot in the passing game—he had just seven receptions in 2018. However, Michel's struggles aren't entirely on him.

The Patriots have been playing with backups at both left tackle and center, and their ground game as a whole has suffered. As the new lineup continues to jell, Michel should start finding the running room he enjoyed in his inaugural season.

Verdict: Sell

Baker Mayfield, QB, Cleveland Browns

Cleveland Browns quarterback Baker Mayfield lit the NFL world on fire last season, passing for a rookie-record 27 touchdowns and almost single-handedly lifting Cleveland into relevance.

This year, however, Mayfield has been a borderline disaster. He's been skittish in the pocket, indecisive with his throws and hasn't displayed the same downfield accuracy that made him a star in 2018. Part of the problem is Mayfield himself, part is the fact that he's playing with a largely new supporting cast—and a new offensive coordinator—and part is that the rest of the league has put a target on him.

"I think they see Baker's name, I think they see him the media, I think they see some of his quotes and things of that nature, and they want a piece of him," Browns guard Joel Bitonio said, per Nate Ulrich of Ohio.com.

It's far too early to panic on Mayfield, though. He's faced some tough competition to start the season, and the offense is still finding its rhythm. However, if he doesn't start trusting his progressions, his offensive line and his receivers more, his struggles are going to continue.

Verdict: Buy

Gus Edwards, RB, Baltimore Ravens

As a rookie, Gus Edwards led all Baltimore Ravens running backs with 718 yards on the ground. He averaged an impressive 5.2 yards per carry and had a long run of 43 yards.

Through five games this season, Edwards has produced just 165 yards at a clip of 4.3 yards per carry. However, his drop-off in production has more to do with the Ravens signing veteran Mark Ingram II than it does Edwards' ability.

The touches simply haven't been there for the second-year back.

"It's just a matter of being put in there, the opportunity and how the flow of the game is going," Edwards explained, per Alex Murphy of PressBox.com.

Should the Ravens call on Edwards to carry the load at any point this season, he'll likely be ready. His lack of production is a source of frustration for fantasy managers, but there's still a lot of time for Edwards to become more involved in the offense.

Verdict: Sell

Antonio Callaway, WR, Cleveland Browns

Browns wide receiver Antonio Callaway has only played in one game this season after a four-game suspension for violating the league's substance-abuse policy. In many cases, that wouldn't necessarily factor into a sophomore slump, but it's relevant for Callaway, who fell in the draft largely because of off-field issues.

Callaway was suspended at Florida for violation of team rules.

On the field, Callaway was a liability in his first game back. The questionable hands he flashed as a rookie apparently are still plaguing him, as one drop last Monday resulted in a goal-line interception for Mayfield.

"It's catastrophic. It completely changed the game," offensive coordinator Todd Monken said of the drop-turned-interception, per Mary Kay Cabot of Cleveland.com.

The reality is that Cleveland is going to find it difficult to trust Callaway this season, both on and off the field. Don't be surprised if he becomes an afterthought in the offense once fellow wideout Rashard Higgins returns from injury.

Verdict: Buy

Roquan Smith, LB, Chicago Bears

Chicago Bears linebacker Roquan Smith wasn't active for Week 4, though it still remains unclear exactly why.

"He's completely a personal issue," head coach Matt Nagy said, per ESPN's Jeff Dickerson. "For us, it's something that we're gonna leave it at that right now."

Bears fans may wonder why Smith didn't play, and they may be wondering why he hasn't produced as many impact plays on the field this season. The tackles have been there—he has 33 in four games—but the game-changing plays have not.

As a rookie, Smith produced 5.0 sacks, five passes defended and an interception. He hasn't posted a stat in any of those categories yet in 2019.

Fans shouldn't panic about Smith's status or his production, however. Big plays often come in bunches, and as long as Smith is on the field in one of the league's top defensive units, he'll have opportunities to rack them up.

Verdict: Sell

Josh Allen, QB, Buffalo Bills

Buffalo Bills quarterback Josh Allen had 14 turnovers in 12 games as a rookie, and he's on pace to have even more in 2019. Through five weeks, Allen has turned the ball over nine times, and that is worrisome for Buffalo's offense.

The main concern is that Buffalo is built to win with defense, the running game and efficient offense. The Bills want to grind out ugly wins, and that will be difficult when ball-security is an issue.

While Allen has improved in some areas as a passer since entering the league—he's shown better touch and accuracy this season—his decision-making is still lacking. The Wyoming product continues to throw passes that he shouldn't and take sacks and hits that no quarterback should take.

The result has been serious turnover problems for the Bills. They've survived most weeks despite them, but if Allen doesn't put an end to his careless ways, more losses are going to start cropping up.

Verdict: Buy