Top offensive matchup nightmares

Calvin Johnson, Tyron Smith, Charles ClayGetty Images

NFL coaches don't sleep much during the season.

Between film study, game plans, practice and everything else that goes into preparation for Sundays, shut-eye is hard to come by.

It's especially difficult when preparing for certain star players; the kind of rare physical specimens who can leave a coach scrambling for answers before, during and even after the game. With that in mind, let's begin part one of a two-part feature examining the 10 most nightmarish matchups on either side of the ball in the NFL, based largely off of suggestions from NFL sources around the league.

To be clear, these players are nightmarish because of uncommon physical traits. While there is no quarterback better than Peyton Manning or Tom Brady, defenses that can apply pressure and impact the integrity of the pocket have a chance to slow them down because of their limited mobility. Just one quarterback cracked our list, and he just so happens to have the movement skills of a running back and that applies a different type of stress on a defense that Brady and Manning aren't capable of.

Here are the top 10 offensive nightmare matchups in the NFL:

1. Calvin Johnson, WR, Detroit Lions

The most physically dominant offensive player regardless of position, Johnson is an impossible cover and was the most popular response among coaches and scouts consulted. He's built like a tight end at 6-foot-5 and nearly 240 pounds but maintains the track speed he came into the league with. He can stretch the field vertically, win with his route-running skills on the intermediate level and terrorize defenses as a run-after-catch threat on wide receiver screens.

Even as the Lions have gone through a roulette of complementary receivers to try and take pressure off of Johnson, Megatron has breezed past, through and around opposing defenses. He's a one-man wrecking crew; there's simply no slowing down the game's best receiver.

2. Jimmy Graham, TE, New Orleans Saints

Graham's quest to be redefined as a wide receiver this offseason illustrates the difficulty of covering him. He's far too athletic for linebackers to run with, too big for a safety to contain physically or at the catch point, and while then-Patriots cornerback Aqib Talib had success in shutting down Graham for a half last season, that's way too small of a sample size to suggest some sort of kryptonite exists. Graham is at his best in the slot and the red zone, where quarterback Drew Brees can use Graham's natural leverage to target the athletic pass-catcher in isolated man-to-man situations.

3. Adrian Peterson, RB, Minnesota Vikings

In a league in which running backs are seemingly becoming devalued, Peterson remains a cut above the rest. Consider this: if there were ever a time for a defense to expect Peterson to get the football, it would be on the Vikings' first play of the season. And yet, even when likely expecting it, the Lions had no answer for Peterson on the first play of the 2013 season when he scampered 78 yards for a touchdown. That's the AP threat in a nutshell. Peterson has rare leg drive to power through tacklers, speed to hit a home run if he gets to the second level and is a more capable pass-catcher than his seasonal averages suggest (29.4 catches a year).

4. Percy Harvin, WR, Seattle Seahawks

Straight from an NFC personnel man: "He's a hard assignment because he is both quick and fast. He has the speed to stretch field outside and good change of direction for inside routes. [He's] also great with ball in hands on jet sweeps. What makes him even more difficult is how strong and tough he is."

Harvin is compact at just 184 pounds and health has plagued him of late -- he has still played in just two games for Seattle, one of them the Super Bowl -- but we all saw just how dangerous he can be in that second game, when he returned a kickoff for a touchdown to all but end the night for theĀ  Denver Broncos.

5. Brandon Marshall and Alshon Jeffery, WR, Chicago Bears

To be fair, this duo could be separated and each would still have a chance to make the list. But in tandem, the twin towers (each at least 6-3, 215) are as good as any other receiving duo in the NFL. They both can win with size, but each is also so physically tough and strong that he can overwhelm defenders even in tight spaces. Jeffery's uncommon field awareness and body control resulted in no shortage of highlight-reel catches in 2013, while Marshall has been among the steadiest targets in the NFL over the past seven seasons, with over 1,000 yards in each. Marshall is also extremely versatile, and can line up all over.

6. Cam Newton, QB, Carolina Panthers

In a league in which dual-threat quarterbacks are more popular than ever, none scares defensive coaches quite like Newton. He's a threat to throw from the pocket, can zip it on the run, plus he's as good as there is among quarterbacks in the open field. Moreover, he's the best short yardage back -- or at least close to it -- in the game. The ever-present dilemma teams face against Carolina's offense: Do you pressure Newton to prevent him from picking you apart from the pocket, or use underneath coverage players as spies to prevent him from scrambling for big yardage? What he was able to accomplish with a substandard receiving corps in 2013 was exceptional, and at 250 pounds, he's as big as most linebackers he faces.

7. C.J. Spiller, RB, Buffalo Bills

An intriguing pick after last year's down season, what it comes down to for Spiller is speed and catching ability. The Bills probably didn't do a good enough job of manufacturing touches for Spiller on the perimeter last year, but that's where he's at his best. He's an outstanding pass-catcher and route-runner -- he was a temporary wide receiver for Buffalo in 2011 -- making him difficult to account for with a linebacker. We suspect the ankle issue that Spiller dealt with near the outset of 2013 bothered him more than both the team and he let on down the stretch and would expect a bounce-back season in 2014.

8. Rob Gronkowski, TE, New England Patriots

The same logic we apply to Graham works for Gronk: too big for defensive backs, too fast for linebackers. But here's where defenses really sweat over Gronkowski: if they stay in their base defensive formation, that gives the Patriots' passing attack the advantage against inferior pass defense (only four defensive backs on the field). If a team goes small with a nickel package, the Patriots can overwhelm in the running game, as Gronkowski -- when healthy -- is among the preeminent run-blocking tight ends in the game. His physical ability isn't just an advantage in the passing game. He's a complete tight end.

9. Tyron Smith, LT, Dallas Cowboys

It takes a certain type of offensive lineman to even be considered for this list, but Smith is rare. As one NFC defensive coach said, "He's a freak athlete, and strong. He has great recovery and a great punch." Smith stands 6-5 and 318 pounds, and has the athleticism to neutralize speed/quickness rushers and the strength to hold up against power rushers. What's perhaps scariest about Smith? He's just 23 and will start his fourth NFL season in 2014.

10. Charles Clay, TE, Miami Dolphins

The most surprising response I heard from NFL contacts was Clay. He's not nearly the physically dominant player that others on this list are, but he's wildly versatile. He's nearly 260 pounds, plays from the backfield as a short-yardage ball carrier and lead blocker, can play on the end of the line as a tight end, can flex out into the slot and has terrific catching skills. Any player who can align from so many spots leaves a defensive coordinator wondering how best to slow him down.

Others of note: Colts QB Andrew Luck, Eagles RB Darren Sproles, Buccaneers WR Vincent Jackson, Chiefs RB Jamaal Charles