Top seeds Alexander Zverev and Dominic Thiem have both been knocked out of the Canadian Open at the quarter-final stage in Montreal.
Third seed Zverev, of Germany, made eight double-faults in an error-strewn display as he was beaten 6-3 6-3 by Russia’s Karen Khachanov on Friday.
The second-seeded Austrian Dominic Thiem was stunned in 56 minutes with a 6-3 6-1 defeat at the hands of Khachanov’s compatriot Daniil Medvedev.
Medvedev and Khachanov will create Masters tournament history by competing in the first all-Russian semi-final at that level.
The 22-year-old Zverev was erratic in his performance and after double-faulting for a fifth time, he snapped his racket before dropping the first set with a second break.
Khachanov said Zverev did not play at his best.
“I know what he’s capable of but on the other side, I would like to take credit for myself,” he said.
Another double-fault from Zverev handed Khachanov a match-winning break for 4-2 in the second set.
The world No.8 Khachanov faced two break points serving for the match at 5-3, but held on to prevail in 74 minutes.
Top seed Rafael Nadal plays his quarter-final against Italian Fabio Fognini later.