Bryce Petty insists it’s right around the corner — better accuracy, better productivity, more touchdowns and a win. The problem for the Jets’ third-year quarterback is this: What if it’s not? Then what he might see around that corner is a dead end. Petty, who’ll make his third consecutive start when the Jets play Sunday against the Patriots, will walk onto the frigid Gillette Stadium field with the same unwavering positivity he always possesses. It’s one of his greatest virtues. But will that be enough? It hasn’t been so far. Petty cannot think of Sunday being possibly his last chance to prove he’s worthy of being an NFL starting quarterback, because that’s negative thinking and negative thinking can lead to only one thing: A negative outcome. But the reality for Petty is this: Sunday against the defending Super Bowl champions might very well represent a last stand of sorts for him. A last stand in terms of showing the Jets he should be a part of their future. A last stand in terms of him getting another chance to start an NFL game. And perhaps even a last stand in terms of his NFL career. Too dramatic? Not when you consider that every player in the league understands that “NFL’’ stands for two things — “National Football League’’ and “not for long.’’