According to Alaina Getzenberg of the Charlotte Observer, Rivera said, "I thought it would happen at the end of the season."
Panthers owner David Tepper felt he couldn't wait any longer, though, as the Panthers had lost four straight and suffered an embarrassing 29-21 home loss to the now-3-9 Washington Redskins on Sunday to fall to 5-7.
The 57-year-old Rivera spent parts of nine seasons as the Panthers head coach, going 76-63-1. During that time, he led Carolina to the playoffs four times, including three in a row from 2013 to 2015.
In 2015, the Panthers enjoyed one of the best regular seasons in NFL history, going 15-1 and eventually reaching Super Bowl 50, although they fell to the Denver Broncos and their dominant defense. Even so, quarterback Cam Newton was named MVP that season.
Since then, the Panthers have posted just one winning season.
Rivera addressed the media Wednesday and said his goodbyes. Before leaving the podium, he said his greatest missed opportunity was not winning a Super Bowl as head coach of the Panthers:
While Rivera's tenure ended in disappointment, he is not ready to give up on coaching. Per Getzenberg, he said he "absolutely" wants to coach again.
He was dealt a difficult hand in 2019 with Newton missing almost the entire season because of a foot injury. That forced Rivera to turn to undrafted second-year man Kyle Allen, who has been strong at times but struggled at others, including a few weeks ago when he threw four interceptions in a home loss to the Atlanta Falcons.
In addition to finding a new head coach, the biggest decision for Carolina now comes at QB, where the banged-up Newton is only under contract through the 2020 season.
Rivera will not be part of that decision, but given the success he enjoyed in Carolina, there should be some interest in his services, either as a head coach or defensive coordinator.