Belichick added he doesn't believe Newton's injury to be too serious.
The 32-year-old completed 65.8 percent of his passes for eight touchdowns, 10 interceptions and 2,657 passing yards in 2020. He also added 592 rushing yards and 12 more scores.
The Carolina Panthers took Newton with the first overall pick in the 2011 NFL draft. Newton, who had won a Heisman Trophy and national championship at Auburn the year before, played in Carolina for nine seasons.
He made three Pro Bowls and won the 2015 NFL MVP en route to leading Carolina to the NFC title. The team made the playoffs four times under Newton, including three NFC South championships.
The signal-caller only missed five games over his first eight seasons, playing through injuries along the way.
He suffered a torn rotator cuff in 2016 and underwent surgery in 2017, but he suffered a shoulder injury again in 2018 and was shut down for the last two games.
In 2019, Newton aggravated a left foot injury and eventually underwent Lisfranc surgery. He stayed on the field for much of the 2020 season but missed one game after testing positive for COVID-19. He said the condition affected him in other ways, too.
"I was one of the first football players to catch it, and it happened so fast," he told Brandon Marshall on the I Am Athlete podcast, via Christopher Price of the Boston Globe. "When I came back, that's where the lack of an offseason and the lack of time in the system really showed itself. I was behind and I was thinking too much.
"The offense kept going, and I was stagnant for two weeks. It was all new terminology. I wasn't just trying to learn a system for what it was; I was learning a 20-year system in two months."
In March, the free agent signed a one-year contract to return to New England, which in April drafted Alabama's Mac Jones to be its long-term quarterback.