Luke Kuechly, Josh McCown, DeSean Jackson among big Week 1 injuries

NFL football is back, and so are the injuries.

It was a tough Sunday for health, as several key players went down in the early slate of games.

Carolina Panthers linebacker Luke Kuechly, who just signed a monster contract extension this past week, left the game against the Jacksonville Jaguars with a concussion and didn't return.

Cleveland Browns quarterback Josh McCown tried to launch into the end zone but took a shot against the New York Jets and removed from the game — replacing by Johnny Manziel — with a possible concussion.

Another quarterback, the Oakland Raiders' Derek Carr, left the game against the Cincinnati Bengals with a right (throwing) hand injury and went into the locker room before halftime.

Washington Redskins wide receiver DeSean Jackson pulled up lame on a long pass and left the game against the Miami Dolphins with a hamstring injury. He did not return to the contest, which the Redskins lost 17-10.

The New York Jets are concerned about two serious injuries. Cornerback Antonio Cromartie was being tested on the sideline of their game against the Browns with a possible torn ACL; he did not return in the Jets' 31-10 victory. Rookie linebacker Lorenzo Mauldin, making his NFL debut, left via ambulance to a local hospital with a possible neck injury.

Indianapolis Colts wide receiver T.Y. Hilton left the loss to the Buffalo Bills with a left knee injury.

In the afternoon matchup between the Baltimore Ravens and Denver Broncos, Ravens left tackle Eugene Monroe left with a possible concussion. Later in the game, pass rusher Terrell Suggs was carted back to the locker room with a foot injury.

Even officials weren't immune. Line judge Gary Arthur suffered a broken collarbone in the Denver-Baltimore game.

We're barely into the NFL season and already a number of big-name players are dealing with ailments.