The robbery was reported around 3 a.m. near the intersection of Plymouth Avenue and Lobos Street.
The 24-year-old victim was approached by a suspect who demanded his property. The victim refused and began fighting with the suspect, according to police.
During the fight, a second suspect pulled up in a black, two-door vehicle, got out and struck the victim in the head with a baseball bat, police said.
The suspects, described as two men around 20 years old, then took the victim's wallet and fled. They had not been found as of this morning, according to police.
The victim was taken to San Francisco General Hospital to be treated for his injuries, which are not considered life-threatening, police said.
Anyone with information about the case is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411.