Richards, who is owned by just over 5,000 DT coaches, suffered the injury very late in the contest after a collision with Carlton's Brendon Fevola.
Swans club doctor Nathan Gibbs said, "He remained stable when he came off the ground and we didn't have to do an emergency chest decompression.
"We monitored him and got him straight to hospital where he had a chest drain inserted into his lung to reinflate the lung. He is now doing well and his lung is back to two-thirds it's size within ten minutes of the drain being inserted."
Richards will stay in hospital for another 2-3 days, but his recovery will take a minimum of six weeks.