Carlos Alcaraz rolls on at US Open despite 29 unforced errors - ESPN

Carlos Alcaraz moved into the US Open third round on Thursday with an entertaining 6-3, 6-1, 7-6(4) win over Lloyd Harris in a match that also revealed a lack of sharpness the Spaniard will need to rectify if he is to successfully defend his crown.

Some dazzling shot-making from the tournament's top seed had the crowd on its feet, but behind the fun were some worrying flaws, as Alcaraz piled up 29 unforced errors and showed a lack of concentration at key moments.

Even while not at his best, Alcaraz could rely on raw talent and a vast repertoire of shots to see off the 177th-ranked South African. But the 20-year-old will need to improve with rival Novak Djokovic on the prowl for a 24th Grand Slam title and seeking revenge for his Wimbledon loss to Alcaraz.

After the match, Alcaraz focused on the positives, rating his effort as "great" but admitting to a letdown in the third set.

"I think I played great, a great match," he said. "But obviously in the third set he started to play better. I got down a little bit.

"I need extra energy in the third set.

"In the end, I think I played a pretty good match and will try to keep the same level."

Harris is recovering from wrist surgery and has seen his ranking drop, but the big-hitting South African reached the quarterfinals in 2021 and has a few top-10 wins on his resume, including one over Rafael Nadal.

The contest got off to a cautious start before Alcaraz began to settle into the match, taking control of the first set with a break to go up 3-2.

From that point on, he dialed up the pressure and clinched the set with a second break.

Alcaraz continued to dominate in the second but lost focus in the third, committing 16 of his 29 unforced errors, as Harris threatened to take the contest to a fourth set before losing the tiebreak 7-4.

There will be no room for such lapses in the third round for Alcaraz with 26th seed Dan Evans waiting in the wings.

"It's a really tough player, good serve and volley, good net game," Alcaraz said. "It's going to be really tough.

"I will have to return very, very well if I want to win that match."

Jannik Sinner also advanced to the third round with a 6-4, 6-2, 6-4 victory over fellow Italian Lorenzo Sonego.

Sixth-seeded Sinner improved to 10-0 lifetime against his countrymen. He's seeking a deep run at Flushing Meadows after reaching the semifinals at Wimbledon this year and the quarterfinals at last year's US Open, losing to Alcaraz in a five-set marathon after holding a match point.

"I felt now my game has improved a little bit and developed," said the 22-year-old, who won 89% of his first-serve points and was successful in 22 of 25 trips to the net. "Physically, I'm good, and let's see what's coming."

Elsewhere, Jack Draper upset an apparently ailing Hubert Hurkacz 6-2, 6-4, 7-5, extending his return to the tour after being out more than two months with a shoulder injury.

Draper, a 21-year Brit who only came back to the tour in early August, showed no signs of injury with strong serves and groundstrokes, while Hurkacz appeared listless at times and called the courtside medics over during a changeover in the final set.

Alexander Zverev, the No. 12 seed, downed fellow German Daniel Altmaier 7-6(1), 3-6, 6-4, 6-3 on his return to outer Court 17. Zverev was among several players who noticed a scent of marijuana on the court in the first round, describing it as smelling like "Snoop Dogg's living room."

"I think it will stay the weed court for the tournament," he said Thursday.

For Zverev, a US Open finalist in 2020, it marked his fifth straight advance to the tournament's third round. He will face No. 19 seed Grigor Dimitrov, who downed Andy Murray in a convincing 6-3, 6-4, 6-1 victory in Arthur Ashe Stadium that included 45 unforced errors from Murray.

In other action, Stan Wawrinka, a 38-year-old owner of three major titles including the 2016 US Open, also moved into the third round, beating No. 30 seed Tomas Martin Etcheverry 7-6 (6), 6-7 (7), 6-3, 6-2.

In the day's final match, which ended after 1 a.m., 2021 US Open champion Daniil Medvedev beat Christopher O'Connell 6-2, 6-2, 6-7 (6), 6-2.

Reuters and The Associated Press contributed to this report.