Even when they've made it big in the NFL, young football players aren't finished products. Players might peak earlier in this sport than others (looking at you, baseball), but it usually takes a few seasons at the professional level to become totally refined.

And many, of course, never do.

Fourth-year players are usually pretty polished and aren't likely to change much more, and rookies have yet to truly show us what they'll have to work on to succeed in NFL games. So let's look at the top second- and third-year players and analyze what they need to improve on in 2017 and beyond.

Honorable Mentions

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These are the guys who have been just so damn good that it's tough to find a flaw they "must" fix. But because no player is perfect, there's still something for them to work on...

New York Jets DT Leonard Williams

A strong, technically sound, run-stuffing defensive tackle who is coming off a seven-sack season in which he took just one penalty? This might be my biggest challenge yet.

Could Williams get slightly lower at times? I guess. Does it matter? Probably not. Could he become a stronger pass-rusher by adding more moves to his repertoire? I suppose. Will not doing so prevent him from becoming a superstar? Nope. In fact, I'm pretty sure the primary reason why he sometimes goes long stretches without applying pressure is because that's not really his job most Sundays.

The 23-year-old is going to be a perennial All-Pro regardless, but technically his pass-rush game isn't flawless.

New York Giants S Landon Collins

Collins did it all in his second season with the Giants. Five picks, four sacks, 125 tackles. That earned the 23-year-old a first-team All-Pro nod and nine Defensive Player of the Year votes (third behind Khalil Mack and Von Miller).

He doesn't have to do anything to continue on his current path to stardom, but he did get beat quite frequently in coverage. He was rarely beat deep but was burned by a few receivers and tight ends and gave up a high percentage of completions in general.

It's something he could benefit from working on.

Arizona Cardinals RB David Johnson

OK, here's a nitpick: Johnson isn't a superb blocker. He isn't bad, and he has improved. But it's not an area of strength, and it's something he could manage to get better at. For a dude who can run, catch and score as well as anyone in the game, that's about all I've got.

Tennessee Titans QB Marcus Mariota

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You could argue that Marcus Mariota's top priority should be getting and staying healthy, but that's not totally under his control. He missed four games due to separate knee injuries as a rookie in 2015 and broke his leg near the end of the 2016 campaign, so durability is a concern.

But on the field, Mike B. Herndon of Music City Miracles noticed something interesting about the directional passing numbers listed for the Titans at NFL Savant: Mariota is the anti-Derek Zoolander of the NFL.

He can't throw right.

Per Herndon, Mariota completed just 52.5 percent of his passes to that side of the field last season, which was better than only Cam Newton of the Carolina Panthers.

"I believe Mariota’s struggles throwing to his right are real, and I think they are primarily caused by his footwork when throwing to his right," wrote Herndon. "When throwing to his left or over the middle he does a good job of getting his feet balanced and his shoulders pointed towards his target. This seems to break down a little bit when throwing to his right as he tends to leave his shoulders open and flick the ball to the outside which leads to some high throws as he is unable to get on top of the ball and drive through it."

Mariota still completed 61.2 percent of his passes last season. Imagine how much better he could be if he could correct the problems he's had while throwing right.

Tampa Bay Buccaneers QB Jameis Winston

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This is pretty straightforward and is not unusual. Jameis Winston has thrown 33 interceptions two years into his career. That number is too high, and it's a tad concerning that 18 of those picks came in his second season.

Twenty-one of those picks have come in one-score games, which reinforces the notion that the 2015 No. 1 overall pick presses too hard at times in big moments.

The good news is it's not uncommon for quarterbacks to deal with problems like these early in their careers.

Just ask Peyton Manning.

Dallas Cowboys QB Dak Prescott

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Dak Prescott posted the highest qualified rookie passer rating in NFL history in 2016. As a result, you really feel like you're nitpicking by identifying a so-called flaw in his game. But if there's one thing the reigning Offensive Rookie of the Year can improve, it's his improvisation.

I'm not referring to his ability to improvise when plays break down, because that didn't seem to be a major issue for him in 2016 (and it helped that plays rarely broke down in that offense). Instead, I'm talking about his ability to adapt when smart, strong defenses throw new and unexpected elements at him.

For evidence, look at Prescott's two worst performances of the 2016 season, which came in back-to-back weeks against the Minnesota Vikings and New York Giants.

"Against two coordinators who like to confuse a quarterback, Mike Zimmer and Steve Spagnuolo, Prescott struggled when defenses acted in an unusual manner," former NFL quarterback Sage Rosenfels wrote for The Score. "Both defensive coaches called multiple blitzes with defensive linemen dropping into coverage. This is known as a "zone dog." As a young quarterback, you focus so much on safeties and linebackers that many times you miss the subtleties of a defensive end who's light in his stance or a safety blitzing with zone-dropping players behind him. This higher level of football takes time to understand and master."

That's something he and head coach Jason Garrett have surely been working on this offseason.

Philadelphia Eagles QB Carson Wentz

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A lot was made of a December report from Yahoo Sports' Charles Robinson that stated NFL evaluators saw issues with Carson Wentz's throwing mechanics, but Jeff McLane of the Philadelphia Inquirer later reported those problems may have stemmed from soreness in his throwing elbow.

McLane also reported the 2016 No. 2 overall pick "focused on footwork" this offseason, which is important because that was actually his most glaring flaw in 2016. As Bleacher Report's Doug Farrar highlighted in December, Wentz's footwork was often a mess while trying to navigate the pocket and deliver the ball while under pressure last season.

Mechanical issues are a lot tougher to overcome than problems with decision-making or improvisation, so Wentz struggling with pocket mechanics is no joke.

Los Angeles Rams QB Jared Goff

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Jared Goff had a messy rookie season, and we're only talking seven games. But his biggest problem was probably his inability to get rid of the ball and make plays under pressure. And that's not surprising considering there were questions about how he reacted to pressure before he came into the league.

Goff was sacked on 11.3 percent of his dropbacks, which was by far the highest qualified mark in the NFL. And that came after he took 81 sacks and lost 11 fumbles during his three seasons at Cal.

New Pro Bowl left tackle Andrew Whitworth should help, but Goff simply has to be better under pressure.

Dallas Cowboys RB Ezekiel Elliott

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Sadly, at this point, Ezekiel Elliott's largest (only?) issue is his behavior.

ESPN's Adam Schefter reported the superstar running back could be facing a short suspension stemming from an alleged domestic violence incident last July. He's also facing a misdemeanor conviction for speeding, and he was allegedly involved in a fight at a Dallas-area bar earlier this month. Throw in an incident in which he pulled a woman's shirt down at a St. Patrick's Day party, and there have to be questions regarding his maturity.

The trend is troubling. Promising careers have been ruined after similar patterns have developed.

Chicago Bears RB Jordan Howard

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Like David Johnson (and most young running backs), Jordan Howard could improve his blocking. But it might be more pressing for the 2016 rushing title runner-up to work on his receiving skills. He caught just 24 passes in three years in college and dropped seven of the 50 passes thrown his way as a rookie, catching just 29.

According to FoxSports.com, no other running back dropped as many balls.

Howard told me last year that he knew he still had a lot of work to do, and his position coach at Indiana, Deland McCullough, noted Howard had the right mentality for continued improvement.

"He's a guy who's never satisfied, who's continually growing and critiquing himself," McCullough said. "He'll never get the big head, and he'll just keep on coming. Because he knows he'll have to keep proving himself."

Los Angeles Rams RB Todd Gurley

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Todd Gurley was one of the best offensive players in football as a rookie in 2015 and one of the worst as a sophomore in 2016. What happened? He didn't have a lot of support from an offense that struggled to move the ball through the air and didn't have strong line play, but that was also the case in 2015.

Looking at the tape, though, it often felt as though a seemingly frustrated Gurley was either failing to see holes or neglecting to wait for them to open up. His vision and his patience weren't there, and his primary priority this offseason should be to re-establish both of those traits.

A new offense could help him get there, and it's promising that Gurley told Zig Fracassi of SiriusXM NFL Radio (via Jeremy Bergman of NFL.com) earlier this month that he's "definitely been loving" new head coach Sean McVay's system.

Los Angeles Chargers RB Melvin Gordon

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Melvin Gordon got too cute when he broke into the league in 2015, and his lack of aggression led to a poor rookie season in which he scored zero touchdowns on 184 carries. But he fixed that last year, hitting holes with intensity in a breakout sophomore campaign.

Now, he just has to prove he can make it through a full season.

He was placed on injured reserve after tearing the meniscus in his left knee in Week 15 of his rookie campaign and then sprained the PCL in the same knee in 2016, costing him three games. So durability is a bit of a concern, and something the solid young back could use a boost with.

Miami Dolphins RB Jay Ajayi

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Jay Ajayi's second NFL season was phenomenal. He was just the fourth player in NFL history to rush for 200-plus yards more than twice in a single season (the other three: Earl Campbell, O.J. Simpson and Tiki Barber). But he was often all-or-nothing, so he'd benefit from becoming more consistent moving forward.

Rather astonishingly, the 24-year-old Boise State product rushed for fewer than 80 yards in 11 of his other 12 games, and he averaged less than 3.7 yards per carry in six of those outings.

All in all, 49 percent of his 1,272 rushing yards for 2016 came in three games. In the others, he averaged just 3.7 yards per attempt. You can't take those special performances away, but right now, you can't expect them to take place every week.

Oakland Raiders WR Amari Cooper

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Of course, Jay Ajayi isn't the only young NFL star who could manage to be more consistent. The same applies to Amari Cooper, who has already become a regular Pro Bowler two years into his NFL career but has a tendency to disappear at times.

In 2016, for instance, the former No. 4 overall pick was one of just three receivers to total more than 125 receiving yards in four separate outings, but he was also held to fewer than 50 yards on six occasions. He had just two catches in a big December game against Buffalo and caught just a single 28-yard pass two weeks after that.

Receivers are going to have off days. Even the best of 'em. But Cooper has to find a way to reduce the number of disappearing acts.

Kansas City Chiefs WR Tyreek Hill

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Hill made NFL history as the first player to score at least three touchdowns in the roles of receiver, runner and return man last year despite the fact the 23-year-old was the 164th selection in the 2016 NFL draft.

The draft-day slide came after Hill was arrested for assaulting his pregnant girlfriend and Oklahoma State dismissed him from the football program. He pleaded guilty to the assault in 2015 and was sentenced to three years of probation. And that is naturally his biggest issue, but it's in the past and he can't do much about it now.

Instead, he can just stay out of trouble and work on his on-field strength. He's not exactly hard to take down once you get a hand on him, and it's pretty obvious blocking isn't his specialty. That's not what the Chiefs drafted him for, but it couldn't hurt for Hill to continue to add to his already impressive repertoire.

Tennessee Titans OT Jack Conklin

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Jack Conklin was a first-team All-Pro while dominating all 16 games as a rookie at a new position (right tackle versus left, where he played in college) with the Titans. He took just three penalties and was somewhat surprisingly stellar in pass protection in addition to run-paving.

That being said, I still saw a player who had a little bit of trouble with speed rushers (Cameron Wake and Joey Bosa, for example), sometimes resorting to sloppy footwork when seemingly overwhelmed by athletic players on the edge. Those growing pains come with being a rookie, especially in a new spot, but it is something he can work on.

Baltimore Ravens OT Ronnie Stanley

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Ronnie Stanley lived up to his reputation as a refined, elite pass protector as a rookie in 2016, but the Notre Dame product came into the league facing questions regarding his ability to bully defenders and assert himself in the running game. And he didn't do much to quiet those who criticized his run-blocking skills.

He also has to cut down on his penalties after taking eight in just 12 starts as a rookie, but that should come naturally if he can indeed become stronger (literally and figuratively) at paving the way for the Baltimore run game.

Washington Redskins G Brandon Scherff

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Brandon Scherff is coming off a Pro Bowl sophomore season, primarily because he was dominant at opening up holes and protecting quarterback Kirk Cousins at right guard. Again, that's what they drafted him to do, so kudos. But there's always room for improvement, and the 2015 No. 5 overall pick could be more disciplined.

He was penalized eight times (five holding, three false starts), which was tied for the fourth-highest total in the league at that position.

His job is to cut down on the penalties in 2017.

Indianapolis Colts C Ryan Kelly

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Ryan Kelly's rookie campaign was a success. He started all 16 games, shoring up the middle of an offensive line that had been in search of that kind of stability for quite a while. But he's not a superstar yet, and in order to get there, the Alabama product has to become more consistent from week to week.

He shined in Houston, Minnesota and Tennessee but struggled quite a bit against San Diego, Chicago, Kansas City and the new York Jets.

Kelly appeared to realize as a rookie that he wouldn't get weeks off, which is a good sign.

"Every week you've got to bring it," Kelly said after the season, per AL.com's Mark Inabinett. "I think that's something new at the NFL, too. At the college level, you might be playing an elite guy once every three or four weeks. It's every week in the NFL."

Los Angeles Chargers DE Joey Bosa

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Joey Bosa was the Defensive Rookie of the Year despite playing in just 12 games last season, so this is no easy task. The stud rusher had 10.5 sacks in those 12 outings, which is remarkable considering he wasn't with the team during training camp.

When Bosa came into the league, there was concern that he wasn't the strongest tackler and might have trouble in run defense. I didn't see that at all in 2016. Instead, the primary "concern" on my end was the fact that he collected seven penalties in those 12 contests.

Six came for jumping too early, which might be a reflection on his lack of prep prior to his rookie campaign. Still, Bosa has to make an effort to draw fewer flags in 2017.

Jacksonville Jaguars DE Dante Fowler

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This one's easy: Dante Fowler has to stay on the field and out of trouble.

A torn ACL forced the 2015 No. 3 overall pick to miss his entire rookie season, and then he recorded just four sacks over 16 games in 2016. Year 3 isn't off to a much better start, as he was charged with misdemeanor simple battery and mischief two weeks ago.

Now there is even more cause for concern after Greg Auman of the Tampa Bay Times reported the arrest was Fowler's second in the span of 16 months.

We know he has the ability, but a football player not being able to compete for his football team is a fatal flaw.

San Francisco 49ers DE DeForest Buckner

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DeForest Buckner is physically marvelous, and as a rookie he frequently flashed the size, strength and athleticism that caused the 49ers to draft him seventh overall in 2016. But he came into the league a little raw, and it showed.

His technique simply needs work. Balance, footwork, pad level, hand placement. He needs more polish.

It didn't help that Buckner admitted to being "dead tired" at times as a rookie, per Matt Barrows of the Sacramento Bee. But it's a new year, and he's working in a new scheme (in which he'll at least face fewer double-teams). That combined with more experience should help the 23-year-old quite a bit.

Atlanta Falcons OLB Vic Beasley

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Vic Beasley may have led the NFL in sacks as a sophomore in 2016, but the 2015 No. 8 overall pick out of Clemson quite simply needs to become a more well-rounded front-seven defender.

In other words, he has to improve against the run. He doesn't excel at shedding blocks or making tackles in the running game. And while that might not be what Beasley was drafted to do, it would be nice for the Falcons to feel as though they could rely on him to be an asset every down.

There's a chance he never becomes a strong run defender, but the goal should be to become more consistent and less of a liability in those situations.

Chicago Bears OLB Leonard Floyd

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Leonard Floyd has a ton of natural talent, but he has to work on his body.

Concussions are also a concern after the No. 9 overall pick suffered a pair of them as a rookie in 2016 (the second of which took him two months to recover from, according to Patrick Finley of the Chicago Sun-Times), but weight and muscle mass have always been a bit of an issue for him.

The good news is he's put on weight this offseason, according to Adam L. Jahns of the Sun-Times, and it doesn't sound as though concussion symptoms have lingered into camp.

Kansas City Chiefs CB Marcus Peters

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Marcus Peters is one of just six players since the 1970 merger to record 14 or more interceptions two seasons into his career, and he's got two Pro Bowl nods to show for it.

But the 24-year-old former first-round pick has also been flagged for 15 penalties thus far. It sometimes feels like he loses control, which is something that can't happen if he's going to continue to evolve toward superstardom.

Jacksonville Jaguars CB Jalen Ramsey

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Jalen Ramsey had an even bigger issue with penalties as a rookie, drawing 11 flags in 16 starts last season. And two were for unnecessary roughness, which indicates the 22-year-old wasn't just taking penalties because he wasn't up to speed early on.

He needs to learn to rein himself in, and he should also work on his ability to make big plays. After all, the 2016 No. 5 overall pick has intercepted just five passes since enrolling at Florida State in 2013.

New York Giants CB Eli Apple

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Apple had a decent rookie season in coverage, but the Giants would probably like to see him make more plays on the football.

His anti-ball hawk mentality was a bit of a knock on him coming out of Ohio State, and he intercepted just one pass in 14 games (11 starts) in 2016. That's after picking off only four passes in 28 games with the Buckeyes.

To become a star, he'll still have to improve his coverage and tackling skills while cutting down on penalties. But those things usually come with experience. Making game-changing plays is a little tougher to learn.