Officers say the victim was near Fresno and Lewis Streets just after 10 p.m. when he felt a pain in his leg.
He stopped and saw he had been shot in the shin.
Police canvassed the area overnight, looking for clues and asking nearby residents for home security video.
A woman reported hearing a loud noise nearby.
"She heard a shot from the field, she didn't see anybody, but she did hear a shot from the field... at this point, that's all we have," said Fresno Police Lt. Tim Tietjen.
The victim was taken to the hospital and is expected to make a full recovery. Police say he is not cooperating with the investigation.
At this time, it's unclear if the shooting was gang-related. Police have not yet released a suspect description.