A 16-year-old boy was punched in the face and robbed of his mobile phone while playing football with his friends.
The attack happened on Friday at around 9pm in a field at Fullers Slade.
A teenager, also 16, from Milton Keynes was arrested the following day on suspicion of robbery and bailed until June 24.
Officers are investigating and appealing for any witnesses or anyone with any information about the incident to call the 24-hour Thames Valley Police enquiry centre on 101.
If you don’t want to speak directly to the police, you can contact the independent charity Crimestoppers anonymously on 0800 555 111 or online at Crimestoppers.
No personal details are taken, information is not traced or recorded and you will not go to court.