Roger Federer says he was one mistimed blink away from making a quarter-final exit at the Australian Open.
The 20-time Grand Slam-winning Swiss saved seven match points as he battled from 2-set to love and 6-3 down to beat Tennys Sandgren 6-3, 2-6, 2-6, 7-6 (10-8), 6-3 and set up a semi-final with defending champion Novak Djokovic.
"I was definitely incredibly lucky today", Federer told the media after his victory.
The 38-year old had come to accept the 4th set would be his last in this year's competition, adding, "only maybe when I won that 4th set really did I think that maybe this whole thing could turn around.
"I thought he was serving well, it was difficult for me to create chances."
Federer was dealing with a groin issue that he described as "pain and problems" which derailed his game starting from midway through the second set.
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He hopes the tightness he was feeling was merely down to playing a lot, or nerves, but will assess further prior to that showdown with Djokovic.
Federer appeared surprised that he'd overcome as many as seven match points during the course of the 3-hours and 31-minutes on the Rod Laver Arena, saying "I could have blinked at the wrong time and shanked and that would have been it".
World number 100 Sandgren says Federer's determination was a huge factor in the result, "It just seemed like his level picked up when his back was right up against the wall.
"He just wouldn’t give me anything. Credit to him, for sure."
Federer had huge sympathy for Sandgren, "that's why I feel a bit bad in a way because I didn't feel that he did anything really wrong, it's just luck at some point.
"I've been on the other side as well so these ones sting and they hurt.
"If he could obviously play them [the match points] again, he would play them differently."
Sandgren was more sanguine on those spurned opportunities, particularly as only one match point came on his own serve, "If I had, like, six on my serve, I’d be really pissed off."
Djokovic's passage to the semi-finals was far more straightforward, beating Milos Raonic 6-4, 6-3, 7-6.
Women's giant-killer Ons Jabeur finally saw her run ended by the 14th seed Sofia Kenin.
Having accounted for Jo Konta, Caroline Wozniacki and Serena Williams' conqueror Wang Qiang, Jabeur succumbed to a 6-4, 6-4 victory for the American.
Kenin will play top seed and strong home favourite Ashleigh Barty in the semi-finals.
The Aussie beat last year's beaten finalist Petra Kvitova 7-6, 6-2.