Detectives investigating a fail to stop collision are appealing for information to trace the vehicle involved.
Police were called shortly before 01:00hrs on Monday, 11 June to reports of a collision between a silver Volkswagen Golf and a pedestrian on West Hill just south of the junction with Upper Richmond Road in Wandsworth.
The VW - registration GL67 PZK - was travelling from the direction of Upper Richmond Road and failed to stop at the scene.
Officers and the London Ambulance Service attended.
The 24-year-old pedestrian was taken to a south London hospital where he remains in a stable but serious condition.
Detectives from the Roads and Transport Policing Command are investigating.
A 25-year-old man was arrested later the same day on suspicion of causing serious injury by dangerous driving and failing to stop. He was taken to a south London police station and subsequently released under investigation.
Officers are appealing for anyone who has seen the VW, which would have sustained frontal damage, to come forward. It may have been abandoned on the street.
Anyone who witnessed the collision or has any information about the car is asked to contact the Serious Collision Investigation Unit (SCIU) on 020 8543 5157 or Crimestoppers anonymously on 0800 555 111.