The 20-year-old and a 15-year-old friend were set upon by a group of youths on a football pitch at Glasgow Green.
The older of the two victims was stabbed a number of times, with police treating the incident as attempted murder. He was taken to Glasgow Royal Infirmary. The 15-year-old suffered a minor facial injury.
Detective Sergeant Alex McArthur of Strathclyde Police appealed for witnesses to the attack, which took place at 7.20pm on Saturday, to come forward.