Nick Kyrgios said he was racially abused by a spectator during his semi-final with Andy Murray at the Stuttgart Open on Saturday.
Murray won the match 7-6 (7-5) 6-2 to advance to the final, where he will play Matteo Berrettini on Sunday.
However, Kyrgios had greater concerns as he took to Instagram afterwards to say he was called a "little black sheep" by someone in attendance.
"When is this going to stop? Dealing with racial slurs from the crowd?" he wrote.
"I understand that my behaviour isn't the best all the time – but 'you little black sheep', 'shut up and play' – little comments like this are not acceptable. When I retaliate to the crowd, I get penalised. This is messed up."
Meanwhile, Murray's win saw him reach his first tour-level final on grass since 2016.
The three-time major winner upset Stefanos Tsitsipas in the previous round – his first win over a top-five opponent in six years – and followed that up against Kyrgios with another impressive performance.
"A lot of ups and downs, but I kept going and kept working and finally managed to get to another one. I am proud of the effort I have put in," Murray said after securing the win.
He moves up to 47th in the live ATP rankings – the first time he has been in the top 50 since May 2018 – and his clash with Berrettini will be his 70th career final.
"You're always battling yourself as well as the opponent, it's one of the difficult things about individual sports," he added in relation to Kyrgios' frustrations during the game.
"Nick has the potential to be one of the best players in the world, there's absolutely no question about that. But he obviously got very frustrated in the second set and made it a lot easier for me.
"I'm happy to be in the final. I've played well this week and I've got a great opportunity against Matteo tomorrow."