With NBA legend Gregg Popovich stepping away from coaching duties, Mike Tomlin of the Pittsburgh Steelers now holds the title of the longest-tenured head coach across the four major North American sports leagues.

It's the end of an era in San Antonio as head coach Gregg Popovich steps down from the role after 29 seasons leading the Spurs. While this is a seismic development in the NBA, it also has ramifications that bleed into the NFL as well.

The Pittsburgh Steelers' Mike Tomlin entered rare air on Friday. Now that the San Antonio Spurs' longtime leader Gregg Popovich has stepped down from his role at the helm, Tomlin is officially the longest-tenured head coach across the four major North American sports, as noted by reporter Andrew Siciliano.