World number five Andrey Rublev was sensationally defaulted after being accused of swearing at a line judge in the deciding set of his semi-final at the Dubai Open.

The combustible Russian was trailing 6-5 in the third against Alexander Bublik when he appeared to say something to the line judge.

ATP supervisor Roland Herfel came down to the court accompanied by a Russian speaker, who claimed Rublev had sworn in his native language.

Rublev protested, insisting he was speaking in English, while Bublik also backed his opponent.

“I didn’t say ‘f******’. I swear to God. This is huge. I swear to God,” said Rublev.

The offence would usually merit a warning in the first instance, but the 26-year-old was defaulted by umpire Miriam Bley amid jeers from the crowd in Dubai.

Fellow Russian Daria Kasatkina, the world number 12, called the disqualification “a joke”.

She wrote on X, formerly known as Twitter: “So you can just default a player, take his points and money away, without even checking a video replay???

“What a joke, another confirmation we need a VAR in tennis and electronic line calling on all tournaments.”

It was a controversial end to a tight match, with Kazakhstan’s Bublik progressing to the final 6-7 (4) 7-6 (5) 6-5.

He will face Ugo Humbert after the Frenchman beat another Russian, defending champion Daniil Medvedev, 7-5 6-3.