Each season brings a test for every single player in the NFL. Jobs are always on the line.

But for some, this is amplified all the more heading into 2017.

Some guys are in a contract year and have a lot to prove. Others are young players upon whom the mantle of cornerstone weighs heavy — sometimes too heavy. Then there are the quarterbacks who have a lot to gain, and to lose, this upcoming season.

These 10 players are all facing career-defining campaigns in 2017.

Mike Glennon, quarterback, Chicago Bears

Nobody is going to bat an eyelash if Glennon fails to do anything of consequence in Chicago this season. The Bears drafted his replacement already, and if he stinks, they’ll just hand the keys of the offense to Mitch Trubisky — ready or not.

But if Glennon manages to do some positive stuff and looks like a starting-caliber quarterback, then things get interesting. Not only for the Bears and the rest of the quarterback-needy teams around the league, but also for Glennon himself.

Looking at his contract with the Bears, Glennon will be hauling in almost all his guaranteed cash this upcoming season. Chicago has a built-in out after the 2017 season in which he’ll still cost them money, but not a crushing amount.  So if Trubisky is starting next year (he almost certainly will be unless Glennon is too darn good not to start), then cutting Glennon or trading him is cheaper than keeping him on the roster only to stroll the sidelines with a headset and notepad.

Either he’ll keep his job as the starter in Chicago (not likely at all), will play poorly and end up as a career journeyman backup or he’ll make the case for himself as a legitimate starter for another team.