Nothing is guaranteed more than a year out in the NFL, but for the franchise players at the game’s most important position, reputations can swing on a week-to-week basis. Even among the league’s quarterbacks, there are a number of veterans who enter this season with a little more on the line, whether injuries have thrown a wrench in their upward trajectory or off-field drama has put their on-field performance under additional scrutiny. And with Peyton Manning’s retirement and Tom Brady’s looming four-game suspension, there will be a void on the marquee this year for the quarterback capable of stepping up. This week, SI.com's Don Banks, Chris Burke, Doug Farrar, Melissa Jacobs and Amy Parlapiano each named the quarterback they believe has the most to prove in 2016. Eric Single explores the runner-ups.