49ers Tight End John Frank went to medical school. He retired after fiver years, and winning his first Super Bowl ring as a starter. (He won one his rookie year)
The Giants had another guy in the 1990s who was a real brain. He had been redshirted at a Big 12 school as a freshman so he had one year of eligibility left when he graduated, so he played another season after he graduated and pursued a master's degree in some specialized field of science in his fifth year. They showed his report card on TV during a game, and I didn't even recognize the names of half the classes he was taking. LOL.