World quantity two Alcaraz was enjoying China’s Wu, who belied his rating of 560.
Each gamers produced blistering groundstrokes in a high-quality first set which Wu began strongly.
He had the help of the house crowd and hit some eye-catching pictures, particularly off his backhand.
Nevertheless, his serve got here underneath the better strain, and whereas he managed to get to a tie-break he misplaced it to go a set down.
Within the second set, Wu thought he had saved a break level within the sixth recreation just for his first serve to be deemed out after an Alcaraz evaluate.
The Spaniard then gained the purpose to register the primary break of the match and go 4-2 up, earlier than occurring to serve out the match.
“He is recovering his stage. He is getting back from harm so his stage deserves to be on the high for positive,” stated Alcaraz.
“If he’s nonetheless enjoying at this stage and retains going then I will see him round extra usually.
“I am actually joyful to get via. I am not used to the way in which I felt on court docket. He is a extremely highly effective participant and performed sturdy. I felt like I used to be not dominating the sport.”
Daniil Medvedev additionally made it via, battling to a 5-7 6-4 6-4 victory in opposition to Matteo Arnaldi in two hours 44 minutes.
Medvedev achieved the decisive break within the ninth recreation of the deciding set earlier than occurring to serve out for the match and can play both Stefanos Tsitsipas or Alexandre Muller within the final 16.
“It was a really robust match, a really shut one,” stated Medvedev. “I really felt like that is the place tennis is humorous. I felt like within the first set, I used to be in all probability the higher participant, had extra alternatives. I didn’t handle to [win] it, performed a foul recreation on the finish of the set.
“Within the different units, I believed it was nearer, possibly even he had the sting on a few of the moments. However, that is why tennis is loopy, you may win when you do not count on it, and lose whenever you count on to win, so I’m joyful to be right here once more in two days.”
Play was cancelled on the skin courts for the second day operating due to the rain, with matches solely potential underneath the roof of the primary stadium present court docket.