Officers responded to several reports of yelling and bottles breaking in the 3800 block of Vineyard Avenue at about 5:40 p.m.
Although officers arrived on the scene within four minutes, no suspects or victims were to be found.
Twenty minutes later, an 18-year-old Tracy man arrived at Valley Care Medical Hospital with a non-life threatening stab wound, according to police.
The victim told police his injuries were sustained at the same scene.
Police ask anyone with information to contact the department at (925) 931-5100