Brazilian midfielder Taison was ruled out after reacting to accusations of racist violence during Shakhtar Donetsk's 1-0 home win against Dynamo Kyiv.
Taison, 31, made a gesture to Dynamo fans and threw them the ball before the referee pulled the players out of the field in the 77th minute.
When they came back five minutes later, Taison received a red card.
Shakhtar said Taison and his countryman Dentinho were targeted and that Dynamo supporters have been warned twice.
Video on social media shows the two Brazilians in tears.
In a statement after the match, Dynamo said that they would cooperate with any investigation into the incident.
"It's terrible when such things happen in football," said Shakhtar midfielder Marcos Antonio after the Ukrainian Premier League match. "The game needs real fans instead of those who come into the stadium and behave in this way, without respecting the athletes.
"We have to work on this, because such episodes have all upset us, Dentinho, Taison, the other guys are really feeling terrible right now."
His teammate and goalkeeper Andriy Pyatov added, "Everyone is a little shocked by what happened in the stands today, I saw it for the first time in my life. I never thought that people could behave in this way, flattering someone.
"We discussed the accident with Dynamo players in the players' tunnel and they also have representatives of other nationalities in the team." I saw that [the player of the Dynamo Gerson] Rodrigues was also shocked, because it concerned him. The referee had said that he would stop the match if it happened again. "
Luis Castro, director of Shakhtar, said: "I want to absolutely support all people with racism and people who have suffered today.
"All manifestations of racism are absolutely unacceptable, it has been, is and will be a shame for everyone, together we must fight it – every day, every minute and every second."
In a club statement, Shakhtar stated that they "categorically opposed any manifestations and forms of racism, racial discrimination, xenophobia and related intolerance".
Shakhtar added, "There can be no justification for those who insult other people because of their skin color, their religious or political beliefs.This kind of behavior is unacceptable in all civilized countries and in football leagues.
"Such humiliating accidents cause pain and disappointment to the football family of FC Shakhtar, we condemn this kind of public behavior, we will always express our support and protect our players, we call on the authorities and football clubs to stop racism stadiums. "
In one tweet After the match, Dynamo wrote "#NoToRacism".
"We regard as hasty the allegation of a predetermined guilt of supporters, when the investigation into the circumstances of this case has not yet begun," said Dynamo.
"We look forward to the start of the investigation, ready to assist in depth and, in case of proven guilt, will take all possible measures to further isolate these individuals from football but also from society.
"We look forward to posting photos and videos that will shed light on all the circumstances of the incident."
Mario Balotelli [Brescia] threw the ball into the crowd last week and threatened to leave the field after suffering a 2-1 defeat in Verona.