On 7 October 2018, after Krasnodar's
Russian Premier League game away to
Zenit St.Petersburg, in which Mamayev scored Krasnodar's goal in a 2–1 defeat, Mamayev and
Aleksandr Kokorin traveled to
Moscow for a night out. The following morning both Mamayev and Kokorin are said to have been involved in a drunken attack on Russian Trade Ministry official Denis Pak, resulting in Pak requiring medical attention. As a result, Krasnodar announced that they had imposed the maximum fine they could on Mamayev, removed him from first team training and were investigating how to terminate his contract. Hours before that incident, Mamayev, Kokorin and other young people were involved in an altercation with the driver of a
Channel One show presenter; he received brain damage, nose fracture and face contusions after numerous punches. Mamayev was apprehended for two months. Mamayev remained in prison until his trial, which began on 9 April 2019. On 8 May 2019, he was sentenced to 17 months in penal colony. Considering the time he spent in pre-trial detention, the latest possible date for his release from custody was 13 November 2019. He was released on 17 September 2019. ==Career statistics==