The days when Bob Costas was the face of major sports events on NBC have been waning. Now, they may disappear altogether.

Costas and his representatives are in discussions about terminating a contract that runs through 2021, the New York Post and USA Today reported this week, with Costas telling USA Today that “what was once a perfect fit no longer fits that description.”

Costas, 66, joined NBC Sports in 1979 and has long been a reassuring presence during the Olympics, Super Bowls, World Series and other national events. That role was diminished in recent years after the arrival of Mike Tirico from ESPN, and with Costas’s increasingly opinionated takes on matters like the NFL’s concussion problem and gun violence in America. NBC has not commented on the reports of a pending departure; Costas spoke generally about his career with USA Today on Tuesday.

“There was a very long period of time when NBC’s programming suited my interests and abilities very well, from ‘Later’ [his late-night talk show] to the news magazines to baseball, the NBA and the Olympics,” Costas said. “And after deciding on my own to leave the Olympics after having done a dozen of them, you just look around and say, ‘What was once a perfect fit no longer fits that description.’ ”