Stefanos Tsitsipas and Alexander Zverev have been knocked out of the Indian Wells Masters after both lost their quarter-final matches in California.
Greek world number three Tsitsipas lost 6-4 2-6 6-4 to unseeded Georgian Nikoloz Basilashvili.
German Olympic champion Zverev failed to convert two match points in a surprise 4-6 6-3 7-6 (7-3) defeat by American Taylor Fritz.
Basilashvili will meet Fritz on Saturday for a place in the final.
It is the first time either player has reached the semi-finals of a Masters 1,000 tournament.
French Open runner-up Tsitsipas, seeded second, started in sluggish fashion as he dropped the opening set, managing just eight winners to Basilashvili's 14.
However, Tsitsipas - who won his first Masters 1,000 title at the Monte Carlo Masters in April - regrouped to dominate the second set.
But just when it looked as if the 23-year-old was poised to replicate comeback wins over Fabio Fognini and Alex de Minaur in the previous rounds, Basilashvili secured a break in the opening game of the third and produced some superb winners to upset Tsitsipas.
In Friday's second quarter-final, Zverev was serving for the match at 5-3 up in the third set, only to hit two double faults as Fritz hit back to secure a crucial break.
The 23-year-old eventually forced a tie-break, which he dominated to book his place in the last four.
It was a major shock, with Zverev having won 20 of his past 21 matches on hard courts and searching for his third Masters 1,000 title of the season.
Saturday's other semi-final sees Britain's Cameron Norrie taking on Bulgarian 23rd seed Grigor Dimitrov, who shocked US Open champion Daniil Medvedev in the last 16 on Wednesday.