Tony Romo
The writing was on the wall for Romo after the Cowboys drafted Dak Prescott in 2016. He knew that his NFL career was on borrowed time but he held on for as long as he could. 2015 was a terrible year for the quarterback because he only made four appearances.
But he still opted to return the following year despite being unable to supplant Prescott. Meanwhile, injuries meant that he missed most of the season anyway. Dallas handed him the opportunity to say goodbye to the fans but he should have retired earlier (via Sports Illustrated).