LONDON—After blowout losses to Novak Djokovic and Tomas Berdych at the ATP World Tour Finals, Marin Cilic says his body isn't feeling well. The U.S. Open champion lost 6-1, 6-1 to Djokovic on Monday, and 6-3, 6-1 to Berdych on Wednesday.

“It’s a little bit disappointing to play like this. I was not expecting it. But sort of I feel a little bit tired, and body feels a little bit tired on the court,” Cilic said. “Its seems that the things that I'm doing that are all basically going in a wrong direction. Especially with these guys at this kind of level, even small mistakes, or if you're not at your best performances, the outcome is not going to be going in your favor.”

Cilic won an ATP 250 tournament in Moscow on October 13 but did not play again before this event. Against Berdych, whom he had beaten in the quarterfinals of the U.S. Open, Cilic really struggled, hitting only 11 winners.

“I haven't been playing last few weeks,” he said. “Also the body, of course, is not at the best possible shape. So that's also one of the small parts that have a big part, actually, in the matches. It's unfortunate, as well. I was looking forward to play here, to do well, to play good matches on a high level. But it's a little bit, of course, tough to handle, tough to look at. Both matches I've played, I didn't play on a good level. That's tough to handle, too.”