An accusation of racism after the final whistle on Friday threatened to overshadow Union Berlin's 1-0 home win over Bayer Leverkusen which lifted the hosts to fourth in the table.
Leverkusen midfielder Nadiem Amiri, who was born in Germany to Afghan parents, was booked on 90 minutes and had to be restrained during a heated exchange with a group of Union players.
"Nadiem Amiri's background was insulted. There is no place for that on the pitch here. That is the saddest thing about the whole evening," Leverkusen defender Jonathan Tah told DAZN.
Tah said he heard the insult "shitty Afghan" aimed at Amiri and wants the German FA to investigate.
"I hope there are consequences," he said.
Union coach Urs Fischer, who went to Amiri's aid, said the home side will investigate.
"Words were spoken which had no business being on a football pitch," said the Swiss boss.
"We'll try to sort this out, but if that is the case, then I apologise for it," he added following Tah's allegation.
The incident cast a shadow over Union claiming another major Bundesliga scalp at home, four weeks after an upset win over Borussia Dortmund.
Union's replacement forward Cedric Teuchert sprinted onto a pass which split Leverkusen's defence and fired home the winning goal two minutes from time.
The 24-year-old made amends for squandering a golden chance six minutes after the break when his shot beat Lukas Hradecky, smashed against the post and rolled agonisingly along the goalline and away to safety.
"I don't think any teams like playing us here. It's a lot of fun playing in this team at the moment," said Teuchert.
Teuchert had replaced Dutch striker Sheraldo Becker, who was helped off on 24 minutes with an ankle injury.
On Saturday, RB Leipzig can go top of the table if they beat Wolfsburg.
Leipzig are currently two points behind embattled leaders Bayern Munich, who host Freiburg on Sunday.
Bayern are under pressure after last weekend's league defeat at Borussia Moenchengladbach and the midweek German Cup exit at second division Holstein Kiel.