It was supposed to be a quarterback competition but has turned into a quarterback by attrition.

Geno Smith was given a chance last night to prove he is capable of being the Jets starting quarterback this season. Despite falling way short of doing that he could earn the job by default thanks to a questionable if not boneheaded decision by head coach Rex Ryan.

Smith played like an inexperienced rookie during his three-plus quarters of duty in the Jets 24-21 overtime win over the Giants last night at MetLife Stadium. He threw three first-half interceptions and inexplicably stepped out of the end zone in the fourth quarter giving the Giants a safety.

He looked nothing like a quarterback ready to start the season opener in two weeks against the Bucs which isn’t unexpected. What was surprising was Ryan’s decision to put Mark Sanchez in the game with 11 minutes 21 seconds left in the fourth quarter behind a second- and third-string offensive line. Six minutes later Sanchez was pounded by the Giants’ pass rush and suffered a shoulder injury that could jeopardize his chances of starting the season.

Ryan’s decision to put Sanchez in harm’s way is even more mind-boggling considering how Smith had played. The second-round pick from West Virginia might someday be the face of the franchise and have a long distinguished career. But it’s clear he’s not ready to face a steady dose of NFL defenses.

One play stands out. It was his third interception of the night. It came when Giants defensive end Justin Tuck took his stance on the line of scrimmage looking like he was going to rush the quarterback. Instead he dropped back into coverage. Smith never saw the adjustment and threw the ball right to Tuck at the Giants 34.

In all Smith was 16-of-30 for 199 yards with a quarterback rating of 45.7. He threw one touchdown pass a 22-yarder to Ben Obomanu on the Jets second offensive series of the game.