There has been much speculation over the future of the 25-year-old as he enters the final year of his contract with the Patriots, who drafted Jimmy Garoppolo in the second round of the 2014 NFL Draft as a potential successor to Mallett and starter Tom Brady.
"That's not really something that we're that interested in," Belichick told SiriusXM NFL Radio. "Ryan's done a good job for us.
"Fortunately for us, but unfortunately for him, he hasn't really had any playing time in the last three years. But he's improved tremendously as a quarterback and as a football player, and we've got a lot of confidence in him."
Mallett has thrown just four passes in his three years with Belichick's side.