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.