Novak Djokovic notched his first victory since his shocking third-round exit at the U.S. Open, repeatedly having to battle back to ultimately defeat Alex Michelsen 7-6 (3), 7-6 (9) in their opening-round match at the Rolex Shanghai Masters in Shanghai, China, on Saturday.

After losing the opening three games, the fourth-seeded Djokovic came back to win the first set in a tiebreak. He led 4-1 in the second set before again having to battle back to win on a tiebreak.

The 37-year-old Serbian native and 24-time Grand Slam champion gave credit to his younger competitor, a 20-year-old American with a No. 43 world ranking. It was the first meeting between the two.

"He started terrifically. It was a very close encounter, and I also thought it was a quite a high level of tennis," Djokovic said after the match.

Despite needing "time to get the rust off" after having played only one Davis Cup qualifying match since the U.S Open loss and playing with heavy tape on his right knee, Djokovic was able to take advantage of Michelsen's mistakes for the win.

"I'm just glad to keep my calm when it mattered and glad to be really challenged by a young player," he added. "Now I'm looking forward to the next one."

Djokovic's next opponent will be either Swiss veteran Stan Wawrinka or Italian Flavio Cobolli, who will meet Sunday.

Meanwhile, some of the other top players had an easier time in their opening matches, with top seed Jannik Sinner of Italy and third-seeded Carlos Alcaraz of Spain breezing through.

Coming off a loss to Alcaraz at the China Open on Wednesday, Sinner rebounded with a 6-1, 6-4 victory over Japan's Taro Daniel, notching 12 aces and winning 84 percent of points off his first serve. The match took just one hour and 17 minutes.

Alcaraz needed one minute less to defeat China's Juncheng Shang 6-2, 6-2 for his 10th consecutive win. He's won four titles on the ATP Tour this year, giving him 16 for his career at just age 21.

"I've been playing really good tennis lately, so I want to just keep going and keep feeling it, keep feeling this good," Alcaraz said after the match. "I just had one practice then was straight into this match, so to be able to show this level in the first match, I'm just really proud."

In the next round, Alcaraz will meet unseeded Yibing Wu of China, while Sinner will face No. 31 Tomas Etcheverry of Argentina.

The tournament's No. 2 seed, Germany's Alexander Zverev, also secured a win, beating qualifier Mattia Bellucci 6-4 6-2 in one hour, 36 minutes.

It was the first win in Shanghai since 2019 for Zverev, who withdrew from the China Open last week due to pneumonia.

"I didn't practice, I didn't do anything really. So, of course, I am happy with the level," Zverev said.

Russian Andrey Rublev, the sixth seed, fell to 19-year-old Czech Jakub Mensik, who came back from a 0-2 third-set deficit to win 6-7 (7), 6-4, 6-3.

Mensik's countrymate, Jiri Lehecka, also claimed victory with a 7-6 (6), 6-4 win over Spain's Jaume Munar.

No. 20 Alexei Popyrin of Australia advanced, while No. 32 Brandon Nakashima fell to Japan's Yosuke Watanuki and No. 27 Francisco Cerundolo of Argentina lost to Kazakhstani Alexander Shevchenko, both in two sets.

Three matches on the outside courts -- including those involving seventh-seed Taylor Fritz and ninth-seeded Grigor Dimitrov of Bulgaria -- were suspended due to rain and will be resumed Sunday morning.

--Field Level Media