Tennis news today: Novak Djokovic continues to train during his vacation, Daria Kasatkina back in the top 10 after winning the Silicon Valley Classic

While Novak Djokovic faces an uncertain future with respect to his participation in upcoming tournaments, he's still continuing to train hard. Daria Kasatkina, meanwhile, claimed her first title of the season at the Silicon Valley Classic and is back in the top 10 after three years.

Victoria Azarenka will miss the Canadian Open after her visa wasn't approved. Serena and Venus Williams will be in action on Day 1 of the Canadian Open, and are up against Nuria Parrizas-Diaz and Jil Teichmann respectively. Nick Kyrgios did a clean sweep at the Citi Open by winning the singles and doubles titles.

Here's a round-up of the day's headlines:

Novak Djokovic hits the courts during his downtime in Montenegro

21-time Grand Slam champion Novak Djokovic was ruled out of the Canadian Open due to the country's vaccine mandate. Djokovic's participation in the Cincinnati Open and the US Open remains in doubt as well. Nevertheless, the Serb isn't letting that get in the way of his daily schedule.

Djokovic was seen having a practice session in Montenegro, where he's currently spending time. Politicians in the US are making a push to enable his participation in upcoming events, but whether their efforts will bear fruit remains to be seen.

Daria Kasatkina re-enters the top 10 of the WTA rankings

Daria Kasatkina staged a comeback to defeat Shelby Rogers in three sets and win her first title of the year at the Silicon Valley Classic. As a result, she's back in the top 10 of the rankings for the first time since 2019. Her ranking of No. 9 is a career-high for the Russian.

Kasatkina has put together a consistent season and has the third-most number of wins this year, trailing only Iga Swiatek and Ons Jabeur.

Victoria Azarenka out of the Canadian Open due to visa issues

Two-time Grand Slam champion Victoria Azarenka had to withdraw from the Canadian Open as her visa wasn't approved by the authorities. The Belarusian expressed her disappointment at the latest turn of events, but will be in action at the Cincinnati Open next week.

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Azarenka was drawn against Belinda Bencic in the first round. Had she won her opener, a second-round showdown with old rival Serena Williams would have been a distinct possibility.

Serena and Venus Williams headline Day 1 of the Canadian Open

Fans are in for a treat as the Williams sisters are in action on the very first day of the Canadian Open. Serena Williams will take on Nuria Parrizas-Diaz in the day session. The former World No. 1 lost her comeback match at Wimbledon last month, going down to Harmony Tan in the first round.

Venus Williams will close out the night session and is up against Jil Teichmann. The seven-time Grand Slam champion returned to action at the Citi Open and almost won her match as well. She was leading in the deciding set but Rebecca Marino staged a comeback to defeat her.

Nick Kyrgios completes the Citi Open double

Nick Kyrgios claimed the singles and doubles titles at the Citi Open and became the first player to do so at the tournament. He defeated Yoshihito Nishioka 6-4, 6-3 to win the singles title. He also won the singles title here in 2019. Alongside partner Jack Sock, the duo then beat the pairing of Ivan Dodig and Austin Krajicek 7-5, 6-4 to claim the doubles title.

This was Kyrgios' third doubles title of the season, having won the Australian Open at the start of the year and the Atlanta Open last week.