The AAFC dissolved after the 1949 season, and the Browns were absorbed by the more established NFL. The Browns won the NFL championship in 1950, and advanced to the championship game but lost each year between 1951 and 1953, Thompson's last season. During his last two years, he was the right-side linebacker after Cleveland switched to a 5-2 defense. He was named a second-team All-Pro in 1951 and 1952 and a first-team All-Pro in 1953. Thompson, who was known as a sure tackler and a tenacious leader on defense, was the Browns' team captain in his final two seasons.