Kokorin (left) and Mamaev (right) played together for Russia at Euro 2016
Two Russia internationals could face jail after being charged with hooliganism by Moscow police.
Zenit St Petersburg's Aleksandr Kokorin and Krasnodar's Pavel Mamaev are said to have assaulted trade ministry official Denis Pak on Monday, leaving him needing medical treatment.
Police have detained the pair for questioning and plan to make them meet their alleged victim.
The punishment for hooliganism is a maximum penalty of seven years in jail.
Police said both players had reported to a police station on Wednesday.
They were detained for 48 hours and prosecutors will ask for this to be extended on Friday.
Russia internationals Kokorin & Mamaev should face 'severe punishment'
The pair were on opposing sides in Sunday's top-of-the-table clash between Zenit and Krasnodar, with forward Kokorin, 27, a half-time substitute as league leaders Zenit won 2-1, with midfielder Mamaev, 30, scoring for the visitors.
Meanwhile, Kokorin's stepfather Kirill Loginov has issued an apology published on Kokorin's Instagram page.
"On my own behalf and my son's behalf, I want to apologise for what happened to Denis Pak," he wrote.
"My son sincerely regrets that he hit Mr Pak and, after questioning, he wanted to apologise publicly to him and to all those let down by his behaviour.
"But he didn't manage to do that - he wasn't given that opportunity. That's why I'm doing it for him.
"He's not trying to find some justification, nor am I. Such hot-headed behaviour was unacceptable, his reaction to the insults from Denis Pak was excessively crude, and Sasha acknowledges that fully."
Kokorin also posted this picture with Mamaev on Monday, congratulating Zenit on their win and Mamaev for scoring - on President Putin's birthday
Earlier, in a statement about the players, the Russian Premier League expressed "its outrage and strongly condemns their rowdy behaviour".
It added: "This act not only casts a shadow over the glorious names of FC Zenit and FC Krasnodar, but all of Russian football.
"We believe that those responsible should be punished in the most severe way. There is no place for hooligans in football."
Zenit said Kokorin had behaved "disgustingly" and Krasnodar said they were looking to end Mamaev's contract.
Kokorin has 48 caps for Russia, but missed this year's home World Cup through injury, while Mamaev has 15, with his last international appearance coming in 2016.