Denis Shapovalov accused a match umpire of being "corrupt" over what he thought was Rafael Nadal's slow play at the Australian Open.
Canadian Shapovalov pulled off one of the biggest victories of his career to beat third seed Alexander Zverev in the fourth round to reach his third slam quarter-final and first in Melbourne.
But the 22-year-old was unable to find his best form in the opening set against the Spaniard, though, and then showed his frustration by getting into a row with umpire Carlos Bernardes over the time Nadal was taking between points.
After Bernardes refused to give Nadal a time violation for delaying Shapovalov on his serve, the Canadian shouted: "You guys are all corrupt," and he and Nadal then had words at the net.
It did not distract Nadal, who moved into a two-set lead, but Shapovalov began to turn the tide in the third set and clinched it with a backhand winner after his opponent was given a time violation.
Nadal began to look weary and troubled in the fourth set, leaving the court for six and a half minutes at the end of it for a medical examination and a toilet break.
Two double faults - he served 11 during the match - put him in trouble in the opening game of the decider but Shapovalov could not take advantage and then dropped serve himself to give Nadal a lifeline.
The Spaniard seized it, finding more conviction in his shots again and exploiting costly errors from his opponent, who will feel he had the match in his grasp.
When a final backhand volley drifted wide, Shapovalov smashed his racket angrily on the court while Nadal celebrated reaching his 36th grand slam semi-final.
