Horton's agent, Paul Krepelka, has told multiple media members Horton does not plan to re-sign with the Bruins.
"Nathan has told Boston he wants to move on," TSN's Bob McKenzie said via his Twitter account, quoting Krepelka. "It's not a financial issue, just a decision to move on."
Bruins general manager Peter Chiarelli has said he wants to re-sign Horton, who needs surgery to repair a dislocated shoulder that popped out in the first game of the Stanley Cup Final against the Chicago Blackhawks. He played the final five games of the series with a brace on the shoulder.
Horton, 28, had 13 goals and 22 points for the Bruins in 2012-13, then scored seven goals and had 19 points in 22 Stanley Cup Playoff games. He is coming off a six-year, $24 million contract he signed in 2007 with the Florida Panthers, who traded him to Boston in 2010.