A teenage cricket umpire has allegedly been assaulted by a man drinking at a junior match in Melbourne's west.

Police were called to a reserve in Phoenix Street, Sunshine North, on Friday night after reports a 15-year-old boy had been assaulted.

The boy was allegedly attacked after telling several spectators who were drinking that alcohol wasn't allowed at junior matches.

Witnesses told radio station 3AW the boy was attacked after telling several spectators who were drinking that alcohol wasn't allowed at junior matches.

It is alleged a man in the group headbutted the teenager, who was taken to hospital as a precaution.