NEW HAVEN, Conn. — Madison Keys withdrew from the Connecticut Open after injuring her neck Sunday during a practice session ahead of the tournament she planned to use as a tuneup for the U.S. Open.

Keys said she was hitting a forehand return when she felt pain on the right side of her neck. “I probably hit it late. … As soon as I finished the stroke I knew that I did something,” she said.

Keys, who is ranked No. 9 in the world and seeded third in the tournament, has had trouble with her neck in the past.

She said she would seek medical treatment and hoped to be better in time for the U.S. Open.

“Coming off a good Montreal (tournament) and having a good Olympics, I wanted to have another good week before the Open,” she said.

The 21-year-old American reached the semifinals in the Olympic women’s tennis tournament in Rio de Janeiro, losing to Petra Kvitova of the Czech Republic in the bronze medal match.

Camila Giorgi of Italy replaced Keys in the Connecticut Open field as a lucky loser.

Ekaterina Makarova of Russia beat Sara Errani of Italy 7-5, 6-2 on Sunday; American Shelby Rogers topped France’s Kristina Mladenovic 6-1, 6-1; and Elina Svitolina of the Ukraine edged Daria Kasatkina of Russia 6-4, 5-7, 6-0.

Top-seed Agnieszka Radwanska of Poland and second-seeded Roberta Vinci of Italy have byes to the second round, while defending champion Petra Kvitova and wild-card entrants Eugenie Bouchard of Canada and Caroline Wozniacki of Denmark are scheduled to play Monday.

Czech players Barbora Strycova and Karolina Pliskova also withdrew. Strycova pulled out with an illness and has been replaced by U.S. qualifier Nicole Gibbs. Pliskova, the No. 8 seed, withdrew with a lower back injury. Her replacement in the field will be announced Monday.

CINCINNATI — Tomas Berdych pulled out of the U.S. Open on Saturday, saying he’s been diagnosed with appendicitis and needs time to recover.

The eighth-ranked Berdych lost to Marin Cilic in three sets at the Western & Southern Open on Thursday. He tweeted on Saturday that he was examined in Cincinnati and diagnosed with appendicitis.

“So I will be flying back to Europe for additional checks and treatment,” he wrote on Twitter. “I need to take some time off to recover fully.”

Berdych had his best showing at the U.S. Open in 2012, when he reached the semifinals.

The Grand Slam event also will be missing Roger Federer, who is taking the rest of the season off to rehabilitate a surgically repaired knee. Also, Rafael Nadal isn’t back to full strength after missing two months with an injured left wrist. He returned to the courts, played in the Olympics at Rio de Janeiro, and lost in Cincinnati on Thursday, saying his body was tired and sore from so much tennis after such a long layoff.

Top-ranked Novak Djokovic was upset early in the Olympics and dropped out of Cincinnati because of a sore wrist. Two-time defending champion Serena Williams also dropped out with inflammation in her shoulder.

MASON, Ohio — Karolina Pliskova has reached the Western & Southern Open final for the first time, looking to succeed Serena Williams as champion.

Williams, the two-time defending champ, skipped the tournament with a sore shoulder. The 15th-seeded Pliskova beat Garbine Muguruza 6-1, 6-3 in the semifinals on Saturday.

If Angelique Kerber reaches the final and wins in Cincinnati, she would move ahead of Williams for the WTA’s No. 1 ranking. Williams has topped the rankings for 183 straight weeks, the second-longest such streak.

Andy Murray is the top player left on the men’s side, which was wiped out by injuries. Novak Djokovic and Roger Federer skipped the tournament, and Rafael Nadal was knocked out early as he plays back into shape following a severe wrist injury.