Casper Ruud, a product of Nadal's tennis academy in Mallorca, has beaten top-20 players John Isner and Fabio Fognini to make his mark at the international teams tournament in Australia.
Eighth-seeded Khachanov rallied for a 6-7 (3/7), 7-6 (7/4) 6-2 victory over the volatile Australian, but the final set was close to farce, with Kyrgios engaged in a running dialogue with Irish chair umpire Fergus Murphy.
Rafael Nadal showed no signs of rust as he raced into a 5-0 lead against fellow Spaniard Roberto Bautista Agut in the first set on Court Rainier III, defending his Monte Carlo Masters title with 6-1, 6-1.
Five-time champion Roger Federer beat Australian Nick Kyrgios in three sets and reached the US Open last 16 while Slovakia's Dominika Cibulkova took out Wimbledon champion Angelique Kerber.
The carnage of seeds at the world's premier grass court tennis tournament continued, with only one of the top 10 women's seeds remaining in the tournament at the fourth round.
Second-seeded Wozniacki and 2008 runner-up Jo-Wilfried Tsonga had to come back from big deficits. Wozniacki was 5-1 down and facing two match points in third set while Tsonga rallied from 5-2 down in the fifth set.
A dominant performance seemed to cast aside any doubts there may have been about Rafael Nadal's form brought about by last year's injuries.
Nick Kyrgios said the loss of his grandfather left him perturbed and he wasn't well prepared for the game, smashing his racket into pieces and asking for a beer during the game
Five years ago, there were seven players aged 21 and under who were in the top 150, today that figure has risen to 13.
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