Melbourne - Alexander Zverev almost blew his quest for a maiden Grand Slam title on Thursday before registering a gritty five set win over France's Jeremy Chardy in the Australian Open second round.
The fourth seed looked far from his anointed status as the flag-bearer for the next generation as he failed time and again to put away the veteran before winning 7-6 (7/5), 6-4, 5-7, 6-7 (6/8), 6-1.
The 21-year-old German will face young Australian wildcard Alex Bolt in the last 32 after eventually winning in 3hr 42min on Margaret Court Arena.
Watched by concerned coach Ivan Lendl, Zverev threw away four break points in the third set and four more and a match point in the fourth.
The dogged Frenchman, the world number 36, would not lie down and extended the match beyond midnight with Zverev finally securing match point at 12.15am local time Friday (1315 GMT Thursday).
"Tha was amazing," said Zverev after the pair had embraced warmly at the net. "He's very close to me on tour so it was always going to be an entertaining match."
In-form Zverev began the year with a run to the final of the mixed teams Hopman Cup following his breakthrough victory over Novak Djokovic at the ATP Tour Finals last season.
But he knows he needs to win a Grand Slam soon to cement his place as a serious contender to end the major monopoly enjoyed by the old guard of Roger Federer, Rafael Nadal and Djokovic.
So far, he has reached just one quarter-final in 14 appearances on the game's biggest stages, losing to Dominic Thiem in the last eight at the 2018 French Open despite having won 10 ATP titles.
He has never got beyond the third round in Melbourne. Last year, seeded four, he crashed out at that stage to South Korea's Chung Hyeon.
But it was the manner of his win in London in November - dismissing Djokovic 6-4, 6-3 a day after a 7-5, 7-6 triumph over Federer - that had people believing the German had turned the corner and would be a major force in 2019.
Results from Day 4 of the Australian Open on Thursday:
Kei Nishikori (JPN x8) bt Ivo Karlovic (CRO) 6-3, 7-6 (8/6), 5-7, 5-7, 7-6 (10/7)
Borna Coric (CRO x11) bt Marton Fucsovics (HUN) 6-4, 6-3, 6-4
Pablo Carreno-Busta (ESP x23) bt Ilya Ivashka (BLR) 6-2, 6-3, 7-6 (9/7)
Fabio Fognini (ITA x12) bt Leonardo Mayer (ARG) 7-6 (7/3), 6-3, 7-6 (7/5)
Joao Sousa (POR) bt Philipp Kohlschreiber (GER x32) 7-5, 4-6, 7-6 (7/4), 5-7, 6-4
Pierre-Hugues Herbert (FRA) bt Chung Hyeon (KOR x24) 6-2, 1-6, 6-2, 6-4
Milos Raonic (CAN x16) bt Stan Wawrinka (SUI) 6-7 (4/7), 7-6 (8/6), 7-6 (13/11), 7-6 (7/5)
Denis Shapovalov (CAN x25) bt Taro Daniel (JPN) 6-3, 7-6 (7/2), 6-3
David Goffin (BEL x21) bt Marius Copil (ROU) 5-7, 7-5, 6-2, 6-4
Daniil Medvedev (RUS x15) bt Ryan Harrison (USA) 6-3, 6-3, 6-3
Filip Krajinovic (SRB) bt Evgeny Donskoy (RUS) 6-4, 7-6 (10/8), 7-6 (7/2)
Alexei Popyrin (AUS) bt Dominic Thiem (AUT x7) 7-5, 6-4, 2-0 retired
Alex Bolt (AUS) bt Gilles Simon (FRA x29) 2-6, 6-4, 4-6, 7-6 (10/8), 6-4
Lucas Pouille (FRA x28) bt Maximilian Marterer (GER) 7-6 (10/8), 7-6 (10/8), 5-7, 6-4
Novak Djokovic (SRB x1) bt Jo-Wilfried Tsonga (FRA) 6-3, 7-5, 6-4
Alexander Zverev (GER x4) bt Jérémy Chardy (FRA) 7-6 (7/5), 6-4, 5-7, 6-7 (6/8), 6-1
Camila Giorgi (ITA x27) bt Iga Swiatek (POL) 6-2, 6-0
Wang Qiang (CHN x21) bt Aleksandra Krunic (SRB) 6-2, 6-3
Elina Svitolina (UKR x6) bt Viktoria Kuzmova (SVK) 6-4, 6-1
Karolina Pliskova (CZE x7) bt Madison Brengle (USA) 4-6, 6-1, 6-0
Anastasija Sevastova (LAT x13) bt Bianca Andreescu (CAN) 6-3, 3-6, 6-2
Elise Mertens (BEL x12) bt Margarita Gasparyan (RUS) 6-1, 7-5
Hsieh Su-wei (TPE x28) bt Laura Siegemund (GER) 6-3, 6-4
Madison Keys (USA x17) bt Anastasia Potapova (RUS) 6-3, 6-4
Timea Bacsinszky (SUI) bt Natalia Vikhlyantseva (RUS) 6-2, 7-5
Naomi Osaka (JPN x4) bt Tamara Zidansek (SLO) 6-2, 6-4
Zhang Shuai (CHN) bt Kristyna Pliskova (CZE) 6-3, 7-5
Simona Halep (ROU x1) bt Sofia Kenin (USA) 6-3, 6-7 (5/7), 6-4
Venus Williams (USA) bt Alize Cornet (FRA) 6-3, 4-6, 6-0
Dayana Yastremska (UKR) bt Carla Suarez (ESP x23) 6-3, 3-6, 6-1
Serena Williams (USA x16) bt Eugenie Bouchard (CAN) 6-2, 6-2