Serena Williams has tennis fans holding their breath after a right knee injury during her singles comeback match threw her scheduled doubles reunion with her sister, Venus Williams, into serious doubt.

Playing in her first competitive match since stepping away from the sport after the 2022 U.S. Open, the 44-year-old tweaked her knee late in the first set. She ultimately lost the opening-round match to Australia's Maya Joint. The physical toll was clear enough that Wimbledon and WTA medical staff excused Williams from her mandatory post-match press conference.

Her agent, Jill Smoller, shared a bit of positive news, noting that Williams was able to leave the tournament grounds on her own two feet. Smoller also emphasized that Williams is doing absolutely everything she can to get her body right before Friday's doubles match.

Getting back to this point wasn't an easy decision for the 23-time Grand Slam singles champion. Williams admitted she was incredibly conflicted about returning to the grass courts in London, and it took some real self-persuasion to accept the wildcard invitation and put herself back out there.

Now, the clock is ticking. The Williams sisters haven't shared a Grand Slam doubles court since 2022, and their wildcard entry was lined up to be one of the most exciting storylines of the tournament. They have won six Wimbledon doubles titles as a team, so they know exactly what it takes to win on this stage, but it all comes down to how that knee responds over the next 24 hours.

Everyone is waiting to see if the medical team can work some quick magic so the sisters can make their highly anticipated run together.