A 41-year-old patient with no significant past medical history is brought to the Emergency Department after falling to the ground in the middle of a pick-up basketball game with friends. He neither lost consciousness nor hit his head when he fell. As he landed on the ball of his foot after having taken a shot, he recalls hearing a popping sound followed by immediate pain in the posterior right ankle. Physical exam demonstrates edema around the patient's posterior right ankle and tenderness to palpation. He is unable to plantarflex his right foot. What is the most likely diagnosis of his current condition?
1) Achilles tendon rupture
2) Ankle sprain
3) Fracture of the calcaneus
4) Plantar fasciitis