Caroline Wozniacki's week just got weirder.

Days after having to defend her tweets in support of vertigo-infected Jason Day at the U.S. Open golf championship, the No. 5 player in the world withdrew from her semifinals match against Belinda Bencic at the Aegon International, a Wimbledon tuneup in Eastbourne, England on Friday, citing a back injury.

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The Danish star said her back had been troubling her during the week, but got worse before her match against Bencic.

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"Today it stiffened up more, and I felt like I couldn't move the way I wanted to and felt pain," Wozniacki, the No. 2 seed in Eastbourne, told The Guardian. "I felt really bad for the crowd and everyone who had come out, but there's nothing really I could do about it. It's all about just looking ahead for Wimbledon. You know, just get as much treatment as possible and be ready for my first round there. I'm definitely planning on playing Wimbledon.

"I felt it from the last two, three days and the last two matches I have played, as well. Especially in the beginning. But then it kind of warmed up and I felt better. Today it just felt slightly worse, so I just felt like I won't win this way and I can only make it worse."

What made her withdrawal weird was the fact that she was photographed throwing a football on the tennis court before the match. Wozniacki has been linked romantically to Houston Texans defensive end and reigning NFL Defensive Player of the Year JJ Watt, and her interest in football, the American kind, at least, seems to have intensified.

She posted video of herself throwing the football a couple of weeks ago on her Instagram account. She apparently repeated that performance for the Eastbourne crowd.