After days of hinting at their pairing, Serena Williams and Andy Murray are officially teaming up for the mixed doubles competition at Wimbledon. 

On Wednesday, the high-profile duo signed up to be among the 48 teams vying for the win at the historic tennis competition. It was revealed shortly thereafter that the pair will compete against Germany's Andreas Mies and Chile's Alexa Guarachi at the expected opening match on Friday. Williams has won 23 Grand Slam titles—making her the most successful player in the Open era of tennis—and Murray has won three, ranking as Britain's leading player in the same period. 

Earlier this week, Murray attended a press conference where he named Williams as a potential teammate. "I'm definitely playing in the mixed. I have got my partner—well 90 percent sure," he said. "Is it Serena? Possibly. I just need to just confirm it."

Prior to officially confirming their partnership on Tuesday, Williams allocated time during her exchanges with the press to praise Murray's athleticism. "His work ethic is just honestly off the charts. That's something I've always respected about him. His fitness, everything. To do what he's done in an era where there's so many other great male tennis players, so much competition, to rise above it, not many people have done it. He's actually one of the few."

She also applauded her doubles partner's efforts to highlight women's issues. 

"You can tell he has a really strong woman in his life," Williams said. "I think, above all, that is just fantastic."

Both players have struggled with health concerns recently, which may have spurred hesitation to add more competitions to their already crowded schedules. Murray underwent a hip replacement surgery in January, and Williams has fought to overcome a knee injury for months.

Williams beat No. 161 Giulia Gatto-Monticone on Tuesday to advance to Wimbledon's second round. Murray will compete in men's doubles alongside Pierre-Hugues Herbert of France on Thursday. 

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