Alex de Minaur’s transformation from serial struggler on European clay courts to impressive contender has continued with Australia’s No.1 reaching the Lyon Open semi-final.

The 23-year-old’s preparations for the French Open couldn’t be going more sweetly as de Minaur enjoyed a swift passage into the last four on Thursday when his quarter-final opponent, Japan’s Yosuke Watanuki retired with a back problem after losing the first set 6-4.

It means de Minaur has now reached a second clay-court semi-final in the space of a month, following his brilliant last-four contest with Carlos Alcaraz in Barcelona where the Sydneysider was beaten after holding match point against the Spanish wonder boy.

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De Minaur had been expected to account for the lucky loser, world No.263 Watanuki, an old rival from his junior days who lies 242 places below the Australian on the ATP computer.

But in difficult windy conditions, Watanuki’s back injury made de Minaur’s passage easier as the Australian eked out and won the only break point of the opening set before the Japanese had to admit defeat to his painful back ailment.

He received a sympathetic response from de Minaur, who consoled him after their handshake.

“Wishing a very speedy recovery to Yosuke, who I know very well from juniors,” said de Minaur.

“It is a tough one. It was very tough, a lot of wind out there. I was happy I kept my cool and did what I needed to do.”

Next up for de Minaur in Friday’s semis will be the rapidly rising Alex Molcan, who beat Argentine Federico Coria 6-3 6-2.

“It will be another tough one. He has been having his best year and I am ready for a battle tomorrow,” said de Minaur of the Slovakian left-hander Molcan, who packs a real punch.