The assault happened in the town centre at around 2.30 am near Station Square and Gerston Road. This was the evening and early morning following the England versus Sweden World Cup football match.
A 24-year-old local man was taken to Torbay Hospital and then transferred to Derriford Hospital.
The offender is white, approximately 25-years-old, with a beard. He was tall and was wearing a black T-shirt.
Anyone who witnessed the incident and anyone with information is asked to contact police on 101@dc.police.uk or call 101 quoting CR/060871/18.
You can also give information anonymously via Crimestoppers on 0800 555 111.
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