MELBOURNE, Australia — It was quite a predicament for Grigor Dimitrov, still basking in his triumph at the ATP Finals as he entered his second-round match at the Australian Open against a young American who had never won a tour-level match before qualifying for the first major of the season.
Mackenzie McDonald is ranked 186th and played college tennis at UCLA. He had never played anyone ranked better than No. 69 before facing the third-seeded Dimitrov on Wednesday.
McDonald broke Dimitrov's serve three times in the fourth set and pushed the fifth beyond 12 games — there's no tiebreakers in fifth sets at the Australian Open — before his first double-fault of the set suddenly gave Dimitrov a match point.
Dimitrov finished it off 4-6, 6-2, 6-4, 0-6, 8-6 as midnight approached.
"Really the game wasn't there today. I wasn't feeling well on the court — fourth set was a disgrace," said Dimitrov, who took Rafael Nadal to five sets in a marathon semifinal in Melbourne last year. "But I won with what I had. That was my fighting spirit.
"He played an unbelievable game (but) experience in the end really helped me."
That seemed to be a theme of Day 3.
Second-seeded Caroline Wozniacki had to save two match points and come back from 5-1 down in the third set to beat 119th-ranked Jana Fett 3-6, 6-2, 7-5. Jo-Wilfried Tsonga, the 2008 Australian Open finalist, rallied from 5-2 down in the fifth to overcome Canadian Denis Shapovalov 3-6, 6-3, 1-6, 7-6 (4), 7-5.
And 38-year-old Ivo Karlovic overcame Yuichi Sugita 7-6 (3), 6-7 (3), 7-5, 4-6, 12-10.
Nadal, the 2017 runner-up, didn't risk any close calls. The top-ranked Spaniard made only 10 unforced errors and had just one hiccup — dropping a service game while serving for the match — in a 6-3, 6-4, 7-6 (4) win over Leonardo Mayer.
"It's an important victory for me," said Nadal, who won the French Open and U.S. Open last year but had his preparation for Australia interrupted by an injured right knee. "After a while without being on the competition ... second victory in a row, that's very important."
In the match preceding Nadal and Mayer on Rod Laver Arena, Wozniacki felt like she was "one foot out the tournament" before winning six straight games to advance.
"That was crazy," Wozniacki said. "I don't know how I got back into the match. I was like, 'This is my last chance.'
"At 5-1, 40-15 ... she served a great serve down the T (and) it was just slightly out. I was kind of lucky."
Wozniacki won the next nine points, and 24 of the 31 points played from the first match point.
She'll next play No. 30 Kiki Bertens.
After his enthralling comeback victory over Shapovalov, highlighted by a between-the-legs shot on an important point, Tsonga will meet 17th-seeded Nick Kyrgios in what shapes up to be an entertaining third-round encounter.
Kyrgios had a 7-5, 6-4, 7-6 (2) win over Viktor Troicki, overcoming audio problems at Hisense Arena and complaining to chair umpire James Keothavong, who ended up turning off his microphone and later being hit in the head by a wayward tennis ball.
Dimitrov's reward for beating McDonald is a match against No. 30 Andrey Rublev, who beat him at the U.S. Open last year and who accounted for 2006 Australian Open finalist Marcos Baghdatis 6-4, 6-7 (5), 6-4, 6-2.
At the other end of the experience spectrum, 15-year-old qualifier Marta Kostyuk followed up her first-round win with a 6-3, 7-5 victory over wild-card entry Olivia Rogowska.
The Australian Open junior champion, who entered the season-opening major ranked No. 521, became the youngest player since Martina Hingis in 1996 to win main draw matches in Melbourne.
Things will get harder for her now. She next faces fourth-seeded Elina Svitolina, who had a 4-6, 6-2, 6-1 win over Katerina Siniakova.
Another Ukrainian, Kateryna Bondarenko, beat 15th-seeded Anastasia Pavlyuchenkova 6-2, 6-3 and will next play No. 19 Magdalena Rybarikova.
Alize Cornet beat 12th-seeded Julia Goerges 6-4, 6-3, ending the German player's 15-match winning streak, and Elise Mertens lost the first five games before beating No. 23 Daria Gavrilova 7-5, 6-3 in a match that finished just before 2 a.m. Those results meant seven of the eight seeded players are out of that quarter of the draw.
French Open champion Jelena Ostapenko struggled at times before beating Duan Yingying 6-3, 3-6, 6-4 and will next play No. 32 Anett Kontaveit.
Among the men advancing were Kyle Edmund, No. 6 Marin Cilic, who next plays Ryan Harrison, and No. 10 Pablo Carreno Busta, who will meet No. 23 Gilles Muller.
McDonald didn't quite get the biggest upset of the day, but he got some valuable experience in front of a big crowd on a
He attacked Dimitrov's second serve and his backhand, turning a potential weapon almost into a liability for the Bulgarian.
"I know how close I was to winning," said McDonald, who had practiced with Dimitrov and Roger Federer in the past, and should rise up the rankings. "But he's a good player, he's been out here a while.
"I was soaking it all in. It was a long match and I enjoyed every single moment of it. I'm super happy about it."
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John Pye, The Associated Press