Putney High Street was closed by police while officers dealt with reports of a fight.
Police were called to the scene at around 2.24am on Sunday (October 22) by London Ambulance Service after a 26-year-old man was found unconscious.
The man's injuries are not understood to be life-threatening, a Metropolitan Police spokesman confirmed.
Police declared the area as a crime scene but the road was reopened just before 12pm the same day.
No arrests have been made in connection with the incident and officers from Wandsworth are continuing to investigate the incident.
The southbound lane in Putney High Street was closed between Werter Road and Norroy/Disraeli Road.
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