United States national team co-captain Megan Rapinoe has said players who are not incensed by racism are "part of the problem."
There has been a number of racist incidents in football throughout Europe since the start of the new campaign.
Brescia striker Mario Balotelli threatened to walk off the pitch after suffering monkey chants last weekend, while an FA Cup qualifying round tie between Haringey Borough and Yeovil Town was abondoned when goalkeeper Douglas Pajetat was subjected to racist abuse last month.
"If there's ever an instance of racism, if every single player on the field is not outraged then to me they're part of the problem," Rapinoe told the BBC.