A couple of months later, he's into a Grand Slam semifinal for the first time.
The 24-year-old Frenchman will next play Novak Djokovic, who is aiming for a men's record seventh Australian title, so things will get tougher.
Djokovic was leading 6-1, 4-1 and his quarterfinal match was less than an hour old Wednesday when eighth-seeded Kei Nishikori retired with an injured right leg, finally succumbing after three of his four previous rounds went to five sets. It gave Djokovic a spot in the semifinals at Melbourne Park for the first time since 2016, when he won his second straight title and his fifth in six years.
"Feels great. This has been my most successful Grand Slam throughout my career," Djokovic said. "Past two years have been a bit tough with the elbow injury and everything.
"Over the past 10 years, I've had plenty of success here. Everyone tries to get their hands on one of the four biggest titles in sport, but Australia has been really kind to me."
Pouille isn't even sure how far he's capable of going. But after losing in the first round on his five previous visits, he knows the trajectory is OK.
"I didn't win a match in Melbourne before," Pouille said. "Now I'm in the semifinals. So just very, very happy."
Pouille fended off a strong comeback from 2016 Wimbledon runner-up Milos Raonic for a 7-6 (4), 6-3, 6-7 (2), 6-4 win, his first in three tries in a major quarterfinal and is first against the big-serving Canadian.
Mauresmo, who won two major titles as a player, including the 2006 Australian women's title, had previously worked as Andy Murray's coach. Pouille said Mauresmo had quickly worked out how to improve his game, giving him confidence.
Some people criticized Murray, a three-time major champion and five-time finalist in Australia, when he first hired Mauresmo. But Pouille hasn't had to contend with that kind of sexist negativity.
"I think times changed. It's a shame that it happened," Pouille said. "Men are coaching women, so why not the contrary? She's a champion. She's a great coach."
The No. 28-seeded Pouille was up two sets and had break points in the seventh and ninth games of the third but Raonic held serve in clutch moments.
Then Raonic rallied, railing against officialdom after getting angry when he challenged a line judge's call as Pouille was serving to stay in the set.
His service return hit the baseline but was called out. When he challenged it, and a replay confirmed his shot was good, chair umpire Nico Helwerth ordered a replay of the point.
Raonic thought he deserved to be given the point and, when he asked why it wasn't awarded to him, told the umpire "because you don't watch, because you're incapable."
Pouille won the replayed point and held serve for 6-6, but Raonic won the first six points of the tiebreaker and eventually forced a fourth set.
It was on serve until Pouille put serious pressure on Raonic's serve and volleys, and broke to clinch the match.
Raonic is now 1-3 in Australian Open quarterfinals, but he had a tough draw at Melbourne Park. He had to hold off Nick Kyrgios in the first round, former champion Stan Wawrinka in the second and No. 4-seeded Alexander Zverev in the fourth.
Raonic said he was disappointed with his serve in the quarterfinals, but not about his challenge in the third set.
For Pouille, the 2016 Wimbledon runner-up had some words of wisdom.
"It's not so much only the opponent you're facing, but it's also the situation, which is a completely new one for him," Raonic said. "I think he has to stay true to himself, try to do the things he does well, really focus on that aspect more than anything else."
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