Every NFL season is full of breakout rookies, players for whom everything seems to come naturally.
Linebackers stack up with the league leaders in tackles, running backs roll up stunning four-digit yardage totals, quarterbacks throw shockingly few interceptions and offensive linemen block like seasoned veterans.
Every season also has its share of sophomore slumps.
Not every rookie who takes the league by storm is destined for the Hall of Fame; plenty of first-year players for whom lightning strikes never manage to catch that lightning in a bottle.
Though every football fan wants to root for kids who splash into the league and show all of the veterans how it's done, many hot rookies never repeat that level of performance.
Whether an actual decline in performance, fans and media being more honest about a player's shortcomings or just a sagging of statistical production, sophomore slumps do happen—and here are the players who'll be afflicted.
All statistics sourced from Pro Football Focus, except where noted. A subscription may be required.
Luke Kuechly defied the odds—and the opinions of some draft evaluators, like Bleacher Report's Michael Schottey—when he stepped into the Carolina Panthers defense and produced like a veteran. Kuechly finished with 105 solo tackles, tied for seventh-best amongst all inside linebackers. Kuechly also tied for first in assisted tackles with 32.
While Kuechly was a tackle machine in 2012, his coverage skills were lacking. Kuechly allowed 81.8 percent of passes thrown his way to be completed, and Pro Football Focus graded him at minus-1.8 for coverage, tied for 35th out of 53 inside linebackers.
In 2013, though, the Panthers will boast a beefed-up defensive line. After adding Star Lotulelei and Kawann Short in the first and second round respectively, there's much more talent and beef up front—and there'll be fewer backs coming through the line for Kuechly to tackle.
While Kuechly will be free to cover the pass and make big plays, he hasn't shown much aptitude for either of those. Watch for opponents to attack Kuechly via the passing game in 2013.
As a blazing-fast deep threat to help Andrew Luck show off his arm strength, T.Y. Hilton was everything the Indianapolis Colts could have asked for in 2012.
With 50 catches on 88 targets, Hilton only snagged 56.8 percent of the passes thrown his way. When Hilton and Luck did connect, though, it was magic: Hilton averaged 17.2 yards per completion, fifth-best in the NFL, and racked up totals of 861 yards and seven touchdowns.
The arrival of free agent Darrius Heyward-Bey, however, should cut into Hilton's numbers quite a bit. Heyward-Bey is bigger, more experienced and has been productive in the NFL despite working in one of the league's worst quarterback situations throughout his still-young career.
Furthermore, Hilton's poor hands and route-running are due to catch up with him; Pro Football Focus ranked Hilton 80th out of 105 qualifying wide receivers in 2012. If Hilton isn't benefiting from all of the deep shots, his numbers will take a serious hit.
When 6'5", 345-pound Cordy Glenn played in the Senior Bowl, I saw a natural right guard. When the Bills drafted him to play tackle, it seemed as though right tackle would be a fit.
When Tim Graham of The Buffalo News reported Glenn would start at left tackle, I was not alone in being surprised. When he got off to a hot start, it was even more surprising.
Though Glenn finished with a nicely positive plus-6.6 overall Pro Football Focus grade, PFF marked him down severely for three of his past seven starts.
As opposing defenses figure out how to attack Glenn, he could be even more inconsistent in 2013—bad news when he's charged with protecting whichever one of three very different quarterbacks could end up starting for the Bills.
When the Tennessee Titans drafted linebacker Zach Brown, they likely knew what they were getting: an exceptional athlete without a lot of polished technique—or run-stuffing experience.
Brown delivered on all counts, playing exceptionally well against the pass and not so much against the run.
Brown was third-best in the NFL when it came to passer rating allowed and held opponents to a minuscule 7.7 yards per completion. Brown snagged three interceptions and broke up two passes to boot.
Nevertheless, Brown did not show well against the run. Brown tied for 11th in the NFL in missed tackles, despite playing only 643 snaps. Brown, per Pro Football Focus, graded 28th-best out of 43 linebackers in stopping the run.
In his sophomore season, Brown will have to improve against the run without giving anything up in coverage to avoid a slump. He'll also have to hold off Zaviar Gooden, who plays the same position—and whom the Titans drafted in the third round.
Cornerback is one of the few positions in the NFL where demanding veteran production from a rookie is still too much to ask.
A lot of craft and technique goes into jamming up and shutting down professional receivers, so it's no surprise that Morris Claiborne showed a lot of inconsistency in 2012—as well as a lot of potential and ability.
As the Dallas Cowboys transition to a Tampa 2 defense this season, Claiborne has tried to change his game by adding bulk, but according to Jon Machota of The Dallas Morning News, defensive coordinator Monte Kiffin thinks Claiborne needs to maintain his speed.
Even if Claiborne himself repackages himself as a perfect Tampa 2 cornerback, the Cowboys will have plenty of issues in the front seven as they make the transition. Even if Claiborne takes the "big jump" he's hoping to, per Calvin Watkins of ESPNDallas.com, David Moore of The Dallas Morning News says Claiborne has a long way to go before he reaches the steady performance level of former Cowboys corner Terence Newman.
Greg Zuerlein made waves around the NFL when he combined his massive leg strength with perfect accuracy—through the first five games, at least.
In Week 6, Zuerlein missed three field goals, which ended "Legatron's" perfect rookie campaign. This started a downward slide that resulted in Zuerlein missing 25.8 percent of his attempts.
For Zuerlein's sake, let's hope he regains last season's early incredible form. If he doesn't, he'll quickly be slapped with the "sophomore slump" label.
The Seattle Seahawks brought in defensive end Bruce Irvin to get to the quarterback. That he did, racking up 10 sacks, 12 quarterback hits and 20 quarterback hurries.
As Irvin saw more snaps later in the season, though, it quickly became apparent that he was a one-trick pony. Irvin registered just eight solo tackles and two assists in 452 snaps.
It's no wonder Pro Football Focus issued Irvin a minus-5.5 run-stopping grade, ranked 53rd out of 62 qualifying defensive ends.
With the additions of Cliff Avril and Michael Bennett, Irvin will likely see even less time in situations that don't suit his strengths in 2013. A four-game suspension for performance-enhancing drug use won't help. He'll have to earn his snaps this training camp or become the victim of a massive sophomore slump.
Most great young quarterbacks have a retrenching year. It's especially true for quarterbacks who start from day one and carry the entire workload.
Most notably, the Atlanta Falcons' Matt Ryan regressed significantly from year one to year two. It's not that the quality of their play falls, but that they take on much more responsibility with the offense.
Robert Griffin III isn't just coming off a high-profile knee injury; he's also entering his second season under head coach Mike Shanahan.
Shanahan (and his son, offensive coordinator Kyle Shanahan) bent over backwards to make Griffin comfortable last season, incorporating large chunks of the zone-read and play-action runs he executed so well at Baylor.
Griffin will have to take on greater overall responsibility, along with more traditional passing responsibilities, his sophomore season, all while relying less on his surgically repaired knee.
It won't mean Griffin is backtracking—just the opposite. His statistics, though, are primed for a step back in 2013.