Brady’s TB12 plan incorporates diet, plyometrics and conditioning into a rigorous workout regimen that he does 4-5 days per week during the off-season, with the diet portion essentially a lifestyle choice year round.
The excercise portion includes about 40 minutes per day of resistance band work, in addition to squats, lunges and planks. In many ways TB12 is similar to the WADS that characterize CrossFit training.
Brady is incredibly dedicated and incredibly fit for his age. He also plays QB, a position that does not require the maximization of strength and muscle mass the same as the other 21 positions on a football field.
But to your point there are other means to maintain strength and conditioning without necessarily lifting weights. We can all remember how Steph transformed her body prior to her jr season at UConn through diet & P90x.
So let me rephrase my comment. Nowadays if you are a serious athlete, you have to train seriously or you are not a serious athlete. The days when pro football players spent more time at the bars than the gym are long gone.