I don't think you all understand how strong a silverback is. Throw the players in a ring with the gorilla and less than 20 minutes to come up with a plan the gorilla demolishes them. The people that are saying the players would to be too many because they can surround the gorilla are not very bright. Only about 5-6 players would be able to get near the gorilla at one time. The question is more like how many waves of 6 football players could take on a silverback gorilla and that number is surely over 4.
Seriously, a male Chimp could probably take on 5 NFL players.