He is not the most athletic of QBs which might have been one of the reasons for his 6th round pick in the NFL draft, but 1) he has one of the most accurate throwing arms in the league. 2) His stats back that up. 3) He has appeared in more superbowls than anyone. Probably player, coach or fan. He has actually won more than any other player has played in. 4) He has a coaches understanding of how the game should be played. 5) He knows what defenses want to know so that they can defend and his pre snap reads has him figuring those out. His post snaps reads helps him figure out those little things that a QB can only adjust to after the snap and the defenses have made their commitments. 6) He is a cerebral QB which he may have even had at the start of his NFL career, but his experience goes beyond most. 7) His stats are largely due to his long career and have allowed those to grow to a level that means anyone that breaks any of them will have to play well into their 40s also.