Belichick told his players during a team meeting Thursday morning.
Newton, 31, is the most accomplished of the trio with Stidham in his second season and Hoyer a journeyman who has started 38 games in 11 seasons with seven teams. Newton has a league MVP and has started a Super Bowl.
Newton spent nine seasons in Carolina before the Panthers released him March 24. He remained on the open market until agreeing to terms on a one-year, incentive-laden deal with the Patriots on June 28.
He now faces the tough task of replacing a legend in New England.
Tom Brady, who now is in Tampa, has started the past 60 games for the Patriots dating to his four-game suspension for Deflategate. He missed only 19 games with the Patriots since taking over the starting job in Week Three of 2001, including 15 missed games in 2008 after injuring his knee in Week One.
The job, though, now belongs to Newton.