Daniil Medvedev was forced to dig deep to fight off a charging Filip Krajinovic on Saturday but came through 6-3 6-3 4-6 3-6 6-0 to extend his winning streak to 17 matches and join the Russian charge into the fourth round of the Australian Open.
Medvedev, who had lost the only previous encounter between the two players at Indian Wells in 2019, breezed through the first two sets but looked seriously rattled when Krajinovic won the third and went up a break in the fourth.
It was the fourth seed's first dropped set of the tournament and he forced his coach Gilles Cervara from the otherwise empty stands at Rod Laver Arena with a couple of vicious verbal volleys before taking an injury timeout.
Krajinovic, who spent his pre-tournament quarantine practising with world number one Novak Djokovic, was unrelenting after finding some success preying on Medvedev's forehand, though, and sent the contest into a fifth set.
"He played unbelievable, especially in the fourth set," said Medvedev. "He raised his level."
Medvedev had never won a five-set match in six previous attempts but a second trip to the toilets did the trick and he broke the Serbian for 2-0 in the decider with a crunching forehand winner.
The 25-year-old faced little resistance for the rest of the match from Krajinovic, who was earlier slapped with a code violation for not wearing a mask when going to the toilet.
Medvedev, who next faces American Mackenzie McDonald, anticipated no problems with his coach after their contretemps.
"He said just before leaving that he's sure I'm gonna win the match but he’s gonna leave me alone to be more calm," he said. "I think it was a good thing to do."
Medvedev joined compatriot Aslan Karatsev in the fourth round after the Russian qualifier manufactured a straight sets upset of Diego Schwartzman on Friday.
Seventh seed Andrey Rublev later made it a trio of Russians in the last 16 with a 7-5 6-2 6-3 victory over 39-year-old Spaniard Feliciano Lopez on Margaret Court Arena.
"I feel physically great, I haven't had long matches so far and I feel fresh," said Rublev, who will next face Casper Ruud with Medvedev looming in the quarter-finals.
Victory for Karen Khachanov over Matteo Berrettini later on Saturday would give Russia an open era record four men in the last 16 of a Grand Slam.
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