Players have taken a knee, unfurled slogans and demanded tougher action only to find soccer — their working environment — remains infected with racism.

The tipping point might just have come, with elite players in Paris taking the ultimate step by refusing to continue playing.

At the end of a year of striking gestures against racial injustice and discrimination, the Champions League produced one of soccer's most powerful shows of solidarity against racism when players from Paris Saint-Germain and Instanbul Basaksehir left the field and didn't return.

“The walk off by both Basaksehir and PSG together lays down a marker in Europe," Piara Powar, executive director of the anti-discrimination Fare network, told The Associated Press. "Many players are fed up with half measures to tackle racism and are more prepared than ever to exercise their right to stop a match.”

The flashpoint came on the touchline 14 minutes into Tuesday's game when the fourth official — Sebastian Coltescu of Romania — was accused of using a racial term to identify Pierre Webo before sending off the Black assistant coach of Basaksehir for his conduct on the sidelines.

"You are racist,” Basaksehir coach Okan Buruk said to Coltescu.

An enraged Webo demanded an explanation from Coltescu, repeating at least six times: “Why you say negro?”

The exchanges were broadcast live around the world from soccer's biggest club competition.

“Why when you mention a Black guy, you have to say ‘This Black guy?’” asked Basaksehir substitute Demba Ba, who is Black.

It is the Fare network that helps UEFA prosecute discriminatory incidents like Tuesday night’s alleged abuse at the Parc des Princes.

“Our colleagues at the Romanian state anti- discrimination organization have confirmed it is racist in Romanian to refer to a player by using his race as an identifier," Power said. “There is no ambiguity. This incident shows the need for much better training of match officials. Unintentional racism is still racism."

While games in nations such as France are being played without fans because of the COVID-19 pandemic, typically the racism has come from the stands.

It is the high-profile incidents that highlight an inadequate response, like in the Portuguese league in February.

When Porto striker Moussa Marega tried to walk off the field after being the target of racist abuse from fans in a game against Guimarães, he demanded to be substituted.

But he faced attempts by his own teammates and opposition players to prevent him from leaving the pitch. Even the referee booked Marega for refusing to continue in the game — the type of action that dissuades players from walking off.

The same Romanian referee who took charge of the game in Paris on Tuesday — Ovidiu Hategan — was also in charge for the 2013 Champions League game when Manchester City player Yaya Toure complained about the lack of action against monkey noises he heard from CSKA Moscow fans.

“If officials cannot set the standards by their own behavior," Powar said, “they cannot be relied on to deal with racism on the pitch or in the stands.”

Referees have often been criticized for not leading players off the pitch, rather than leaving them to take the decision. England decided to continue playing a men's international in Montenegro last year after Callum Hudson-Odoi and Danny Rose were targeted with monkey chants.

The Champions League game that was abandoned in Paris will now only resume on Wednesday with a new refereeing team.

“The players walking off is a step in the right direction," former England and Manchester United defender Rio Ferdinand said on Britain’s BT Sport television. "But it can’t just be left to them." ___

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