Schalke are based in Gelsenkirchen in the German state of North Rhine-Westphalia
A Manchester City fan is in a critical condition in hospital after he was assaulted following their Champions League win over Schalke in Germany.
German police said the 32-year-old man suffered a serious head injury in a violent confrontation with two Schalke supporters inside the Veltins Arena.
"In the skirmish, he received a blow from a fist which knocked him to the floor," police said.
"In falling, he suffered a massive trauma to his skull and brain."
The police statement said the man was treated at the stadium before being taken to a local hospital.
It added: "He remains in acute danger of his life at the present time."
The man's family are being supported by Greater Manchester Police, and members of City staff who have stayed in Germany.
GMP said: "We are aware of an assault that occurred following the Schalke v MCFC fixture.
"We are working alongside the football clubs and German authorities to support their investigation and the man's family.
"We would urge anyone with information to contact us on 101 or via live chat so we can share intelligence with our colleagues in Germany."
City won the first leg of the last-16 tie 3-2.
The Premier League champions took the lead through Sergio Aguero before Schalke went 2-1 up through two Nabil Bentaleb penalties.
Nicolas Otamendi was sent off for the visitors but goals from Leroy Sane and Raheem Sterling secured victory.
