Melbourne - Serena Williams says she is "so proud" of her long-time friend Caroline Wozniacki after the Dane succeeded her to become the Australian Open champion on Saturday.
Williams, who has not played a competitive match since capturing the title at Melbourne Park exactly a year ago, was too on edge to watch.
"I got too nervous to watch but woke up to @CaroWozniacki new number one and aussie open champ," she tweeted soon after the 27-year-old beat Simona Halep 7-6 (7/2), 3-6, 6-4, become the new world number one in the process.
"So awesome. So happy. Are those tears? Yup they are," Williams added, with Wozniacki sobbing after ending a long wait to win a Grand Slam title.
"From a year ago to today, I'm so proud my friend, so proud. Literally can't even sleep now," added the 23-time Grand Slam winner.
Williams was pregnant when she won the Australian Open last January. She gave birth to a girl, Alexis Olympia, last September and married father Alexis Ohanian in November.
She is set to make her return next month at a Fed Cup tie when the United States play host to the Netherlands on an indoor hardcourt at Asheville, North Carolina.
Wozniacki also won praise from Rod Laver - with the court on which she won named after the Australian legend.
"Congratulations @CaroWozniacki - welcome to the Club," he tweeted.
Pam Shriver said on Twitter that it was"a breathtaking final" while Boris Becker stated that "both players deserve all the credit in the world".