The 38-year-old goalie, who led the Bruins to their first Stanley Cup in 39 years last season and won the Conn Smythe Trophy as the most valuable player of the playoffs, is heading into the final year of a contract.
"Tim came to me ... through his agent and said that he's seriously considering taking the year off," Bruins General Manager Peter Chiarelli said on a conference call to discuss contract extensions for a pair of other Boston players.
"So, as of now, I am operating under the premise that there's a strong possibility that he'll be taking a year off and we'd have to go about our business without Tim Thomas."
Chiarelli said he was not certain what led to Thomas's move, but said the goalie indicated his family was first and foremost in his thinking.
Thomas, a four-time All-Star and two-time Vezina Trophy winner as the NHL's top goalie, went 35-19-1 with a 2.36 goals-against average for the Northeast Division champion Bruins in the 2011-12 season.
Chiarelli was hosting the conference call to discuss signing forward Daniel Paille to a three-year contract through the 2014-15 season and forward Chris Bourque to a two-year deal through the 2013-14 campaign.