"I was one of the first football players to catch it, and it happened so fast," Newton said on Brandon Marshall's I Am Athlete podcast (h/t 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."
Newton was placed on the reserve/COVID list after Week 3. Though rescheduling allowed him to miss just one game, he was away from the team while in isolation and went three weeks between game action.
"The offense kept going, and I was stagnant for two weeks," he added. "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."
The 31-year-old already got a late start by signing with the Patriots in late June, while the lack of preseason and limited training camp made the transition harder after he spent his previous nine years with the Carolina Panthers.
Newton still started the season well, producing an 89.7 quarterback rating in his first three games with two passing touchdowns and four rushing touchdowns. He also totaled 397 passing yards in a Week 2 loss to the Seattle Seahawks. However, in the final 12 games of the year, he had only six passing touchdowns with eight interceptions and an 80.6 rating.
He's now a free agent, and ESPN's Adam Schefter reported in January on Sunday NFL Countdown: "It looks like [Cam Newton's] looking for something different, the Patriots are looking for something different. Both sides enjoyed their relationship, but both sides expect that it will take them to a different place and a different direction in 2021, with Cam Newton likely moving on and the Patriots in search of a new quarterback for next season."
Newton had previously signed a one-year, $1.75 million incentive-laden contract with New England in July.