World No.1 Daniil Medvedev said on Sunday that he had no choice but to respond to a tennis spectator who jeered him after his loss last week to Nick Kyrgios in Montreal. 

Video of the incident was posted on social media. Medvedev, speaking Sunday as he prepared to start as top seed at the ATP Cincinnati Masters, declined to elaborate on what he told the young spectator who called him a “loser.” But he said he felt compelled to act when the insult came from the person standing with a group of fans at an entrance to the locker room.  “I was disappointed after losing the match [in three sets to Kyrgios],” Medvedev said.