General manager Chris Ballard met with Gore and told the soon-to-be 35-year-old that the Colts do not plan to re-sign him.
"We had a discussion. We had it multiple times during the season. Frank knows we're at the point where we need to get younger, and I want to give Frank a chance to see what's out there and see if he finishes in a place he wants to finish it," Ballard said Wednesday. "He's a first-ballot Hall of Fame player. He likes it when you're honest with him."
Gore, who said he planned to play in 2018, rushed for 961 yards last season and 2,953 yards and 13 touchdowns while starting all 48 games during his three years with the Colts. He has rushed for 14,026 yards during his career and sits 76 shy of passing Curtis Martin for fourth place on the NFL's career rushing list.
"I am aware that Chris Ballard and Frank did have a discussion once the season was over," Colts coach Frank Reich said, "and out of respect to Frank, so he could know exactly what was going on, Chris was right up front and said that we probably would be moving on to make the roster a little bit younger at that position."
Without Gore, the Colts' backfield features Marlon Mack, Matt Jones, Robert Turbin and Josh Ferguson.