MELBOURNE, Australia -- Carlos Alcaraz cruised into the fourth round of the Australian Open when his opponent, Shang Juncheng, retired early in the third set of their third-round encounter Saturday.

Alcaraz, the No. 2 seed, was leading the 18-year-old 6-1, 6-1, 1-0 when Shang, who had his right thigh heavily strapped from the start, called it a day after just 66 minutes.

"It's not the way you want to move on," said Alcaraz, who missed last year's event through injury himself. "Last year I was watching the matches from my couch, wishing to be in the second week.

"This is my first time in the second week at the Australian Open and it feels special."

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Alcaraz will play Miomir Kecmanovic, who saved a match point as he beat last year's semifinalist Tommy Paul 6-4, 3-6, 2-6, 7-6 (7), 6-0.

American Paul led by two sets to one on Margaret Court Arena and had a match point in the fourth-set tiebreak, but Kecmanovic levelled and then ripped through the deciding set for victory.

"Honestly, I have no idea," Kecmanovic said of his victory. "I guess it was just supposed to be my day today. I had a bit more luck and I played some fantastic tennis at the end. I'm really happy to be in the fourth round again."

No. 9 Hubert Hurkacz saw off No. 21 Ugo Humbert 3-6, 6-1, 7-6 (4), 6-3 to reach the fourth round for the second year in a row. He will play the wild-card entry from France, Arthur Cazaux, who beat 28th-ranked Tallon Griekspoor 6-3, 6-3, 6-1.

The Associated Press contributed to this report.