John Terry used a racist obscenity against Anton Ferdinand after taunts about his alleged affair with a team-mate's ex-partner, a court has heard.
The 31-year-old Chelsea and England footballer is charged with a racially-aggravated public order offence - an allegation he denies.
It relates to a comment allegedly made to the QPR defender when the teams played at Loftus Road last October.
The trial, set to last five days, is at Westminster Magistrates' Court.
If found guilty, the maximum sentence Mr Terry could receive is a £2,500 fine.
Chelsea captain Mr Terry was allowed out of the dock into the well of the court to view footage of the alleged insult.