LONDON—Novak Djokovic celebrated his 800th career victory at Queen's Club today.

The former world No. 1 plans to push buttons renewing his rivalry with Roger Federer and Stan Wawrinka tonight.

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Djokovic, who partnered Wawrinka in doubles at the Fever-Tree Championships, says he will be watching tonight's World Cup E Group match between Serbia and Switzerland—and anticipates some private texting and public social media sparring with Swiss stars Federer and Wawrinka.

"I'm sure there is going to be a lot of texting, private texting and social media texting between all of us tonight," Djokovic said. "Well, I mean, it's pretty big match for both nations. Switzerland has had a great success, you know, lately in football and very solid team. Serbia is just assembling a young team that really is creating a wonderful synergy, and they have played really well first match. It's big occasion.

"World Cup, football is the most popular sport on this planet. We all follow it. We all support our nations and teams. Tennis rivalry has nothing to do with this match tonight, but I'm sure that we are all going to be very excited to see every minute of it."

So who's going to win?

"You know the answer to that question already," a smiling Djokovic told the media. "I know you would like Switzerland to win, but of course I want Serbia to win."