The world No. 1 was due to play in the quarterfinals Friday.
Two-time Grand Slam champion Li Na announced Friday that she is retiring from tennis.
The US Open runner-up is just the third person to be featured on the package.
It was a pretty pointless move, but it was awesome, too.
It appears Serena made good on Wozniacki's post-match request for drinks.
Nishikori is the first Asian male to reach a Grand Slam final.
Wozniacki is still in search of her first career Grand Slam title.
Roger Federer saved two match points while coming all the way back from a two-set deficit to beat Gael Monfils 4-6, 3-6, 6-4, 7-5, 6-2 Thursday night and reach the U.S. Open semifinals for the first time since 2011.
Marin Cilic defeated Tomas Berdych in straight sets in the quarterfinals on Thursday to reach his first-ever semifinals at the US Open.
After a bad-as-can-be start, dropping the first three games, Serena Williams quickly turned things around and stretched her U.S. Open winning streak to 19 matches to get back to the semifinals.