The man attacked a 21-year-old woman woman in Weston Park, opposite the city's Children's Hospital, between 10.35pm and 11pm on Monday.
Officers investigating the attack sealed off the park and adjoining Crookes Valley Park for the majority of yesterday while inquiries were carried out at the scene.
The victim is being supported by specialist police officers.
Witnesses or anyone with information should call South Yorkshire Police on 101.
http://www.thestar.co.uk/news/sheffield-ice-hockey-star-guilty-of-sex-offences-against-girls-1-8350756|Sheffield ice hockey star guilty of sex offences against girls|click here}