Defending champion Daniil Medvedev says fans can expect the unexpected when he meets fellow firebrand Nick Kyrgios in the US Open last 16 in New York.
Both players have a reputation as being combustible and are not afraid to speak their minds to umpires or even fans.
"On the court we never really had any fight or anything, which can change any moment," said Medvedev.
The 26-year-old Russian, who has lost three of the pair's four meetings, added: "You never know what's going to happen in the future, we are both quite electric.
"I don't think we are friends.