Shortly before 10 a.m., two males who are known to hang out in the neighborhood got into an altercation on a T-Third Muni platform at Third Street and La Salle Avenue, police Sgt. Troy Dangerfield said.
One left and came back with a group of friends, then stabbed the victim three times, Dangerfield said.
The suspects fled, and the victim was taken to a hospital. His injuries did not appear to be life threatening.
Dangerfield said this afternoon he did not yet know whether any arrests had been made in the case.
Service on the T-Third line was briefly stopped because police heard the suspect might have fled on Muni, but that turned out not to be the case, he said.