PARIS (AP) — Defending champion Daniil Medvedev stayed in contention for the year-end No. 1 ranking by defeating Ilya Ivashka of Belarus 7-5, 6-4 Wednesday in the second round of the Paris Masters.

The second-seeded Russian squandered three set points at 5-1 in the first set and then allowed Ivashka to rally for 5-5. However, Ivashka then dropped serve with a double-fault and three unforced errors and Medvedev clinched the set with a backhand volley.

The U.S. Open champion broke for a 2-1 lead in the second but then hit double-faults on his first two match points before converting the third when Ivashka sent a forehand wide.

Novak Djokovic, who is also playing in Paris, has a lead of 800 points over Medvedev in the rankings and could clinch the year-end No. 1 this week depending on their respective results.

Earlier, an injured Stefanos Tsitsipas retired from his second-round match while trailing 4-2 against Australian opponent Alexei Popyrin.

The third-seeded Greek leads the ATP Tour with 55 wins this year and was playing his 73rd singles match. However, his form has declined since he reached the French Open final, losing in the third round of the U.S. Open in September and in the second round in Vienna last week.

“I haven’t retired once in my life, and it was something that I had to do today,” Tsitsipas said. “Also I’m trying to be cautious for the next tournament, which is the most important one for me.”

Tsitipas has qualified for the season-ending ATP Finals, an eight-man tournament that starts on Nov. 14. He declined to say what was bothering him on Wednesday but he clutched his right arm several times during the match.

“I have had an issue there for quite a while now,” Tsitsipas said. “It has gotten bigger in the last couple of weeks, so I’m just trying to protect it. I felt the pain playing in the match, and I just don’t want for it to get worse than it is now.”

Americans Taylor Fritz, Marcos Giron and Sebastian Korda caused a few upsets in the second round. Fritz beat fifth-seeded Andrey Rublev 7-5, 7-6 (2), qualifier Giron edged 11th-seeded Diego Schwartzman 7-6 (2), 7-6 (4), and Korda cruised past St. Petersburg Open champion Marin Cilic 6-2, 6-4.

Fritz converted the only break point he earned in the final game of the first set and then saved the only break point he faced at 1-1 in the second.

Ranked 26th in the world, Fritz has been playing well in recent weeks. He beat Alexander Zverev in the quarterfinals at Indian Wells last month and reached the final of the St. Petersburg Open last week. Rublev defeated Fritz 6-3, 6-1 in Dubai earlier this year.

Felix Auger-Aliassime and Pablo Carreno Busta both dropped out of contention for the ATP Finals by losing in the second round, but seventh-seeded Hubert Hurkacz and 10th-seeded Cameron Norrie stayed in the race with victories.

The ninth-seeded Auger-Aliassime lost to Dominik Koepfer 6-3, 7-5, while the 12th-seeded Carreno Busta was beaten by French qualifier Hugo Gaston 6-7 (3), 6-4, 7-5.

Koepfer, who saved seven match points against Andy Murray in the previous round, broke Auger-Aliassime twice in each set, winning seven straight games to take a 3-0 lead in the second.

“Very disappointing. I should have done much better,” Auger-Aliassime said. “He played very well, but I fought against myself at some times.”

Hurkacz beat American qualifier Tommy Paul 7-5, 7-6 (4) while Norrie defeated Toronto runner-up Reilly Opelka 6-3, 6-4. Hurkacz overtook Jannik Sinner in the Race to Turin, virtually taking the last spot for the ATP Finals.

Also Wednesday, the fourth-seeded Zverev downed Dusan Lajovic 6-3, 7-6 (5). The Olympic champion needed a medical timeout at 3-2 in the opening set to treat a neck strain.

The 16th-seeded Grigor Dimitrov rallied past 2018 Paris Masters champion Karen Khachanov 4-6, 6-2, 6-0, Carlos Alcaraz ousted Sinner 7-6 (1), 7-5, James Duckworth beat Lorenzo Musetti 6-3, 3-6, 6-3, and the 15th-seeded Gael Monfils of France overcame Adrian Mannarino 2-6, 7-6 (4), 6-2 to next play Djokovic.

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