Steve McNair
McNair had a fabulous career with the Titans and became one of the most popular quarterbacks in the league. However, he should have retired after 11 seasons with his first franchise. But he decided to play for Baltimore before he retired.
The signal-caller had a reasonable first season with the Ravens but only made six appearances in his second year. He risked severe injuries because he wanted to maximize his career earnings before retirement. The late veteran arguably hung on for too long before walking away from the sport (via Tennessean).