The void in women's tennis just got exponentially larger.
The foot injury that has kept Serena Williams from playing for the past eight months appears to be the least of her worries.
Reports surfaced Wednesday morning that Williams underwent emergency treatment Monday in a Los Angeles hospital to remove a blood clot in her lungs. Williams reportedly suffered from a pulmonary embolism last week, and in the wake of that doctors treated her for a hematoma.
"Tough day …" Serena tweeted Tuesday around 11 p.m., California time.
That would seem to be a massive understatement. While her condition is said to be not life-threatening, spokesperson Nicole Chabot acknowledged she was being monitored at Cedars-Sinai Medical Center.
Where does that leave Serena, with regard to tennis, at 29 years old?
If she is to be out for the season and begin again in 2012 at 30, not in a terribly good place.
Williams attended an Elton John AIDS Foundation Oscars viewing party and later the Vanity Fair magazine Oscars party in West Hollywood on Sunday night, but she wound up in the hospital Monday.
No immediate word on her condition was available. In fact, specific information regarding her tenuous medical condition has been scarce since she was sidelined last summer.
"The first thing is for her to get her health back," ESPN analyst Pam Shriver said. "And I'm sure that's what she's focusing on. You can't say that this is uncharted, because Monica Seles was No. 1 when she was stabbed [in 1993] and forced to leave the game. Justine [Henin] surprisingly retired [in 2008] as the No. 1 player. We've seen that abruptness before.
"The one thing we know is that women's tennis marches on. I noticed at the Australian Open that there was a comfort level without Serena that wasn't there last year. Women's tennis was putting on a new face, and it did it quite well, actually."
For what it's worth, Colorado Avalanche forward Tomas Fleischmann, who suffered from a pulmonary embolism in January, was benched for the entire season.
"The nature of his condition requires him to be on blood thinners for several months and he will be unable to play hockey," Avalanche team physician Dr. David Mellman said at the time.
Tennis, obviously, isn't the contact sport that hockey is, but there may be some instructive parallels.
Williams' last competitive match was July 3, when she won the Wimbledon title in straight sets over Vera Zvonareva. She subsequently cut her right foot in an accident at a Munich restaurant and, after playing an exhibition against Kim Clijsters, shut it down. She has had two surgeries since and was next scheduled to play later in March at the Sony Ericsson Open in Miami, although some tennis observers doubted the unstable condition of her foot would allow it.
Witness the arc of one of her great rivals, Henin. The Belgian left the game after the 2008 Australian Open for nearly two years. Upon her return, she reached the Aussie final in 2010, but an elbow injury at Wimbledon took her out for the season and this year -- at 28 -- she retired a second time, apparently for good.
Serena's sister, Venus, is 30 and has shown signs of physical duress for several seasons now. She hasn't won a major since Wimbledon in 2008 and was forced to withdraw from her third-round match in the 2011 in Melbourne with a right hip injury.
How big a presence is Serena Williams in women's tennis? She has won 13 Grand Slam singles titles -- only five fewer than all other active female players combined, including Venus (7) and Clijsters (4).
Serena's potential absence, even for the rest of the season, opens up opportunities for No. 1-ranked Caroline Wozniacki, No. 3 Zvonareva and No. 4 Samantha Stosur, who are all still looking for their first majors.
Serena, currently ranked No. 11, would completely fall off the WTA rankings board if she fails to play by Wimbledon.
A few weeks ago, U.S. Fed Cup captain Mary Joe Fernandez was musing about the women's game.
"We've got to start preparing for life after the Williams sisters," Fernandez said. "You can't deny the fact that their bodies are breaking down."
On Wednesday, Fernandez sounded concerned.
"It's scary," she said. "I'm just praying she's OK. There's so much we don't know at this point. I think, though, her intention will be to play. I know from experience that it's hard to come back from injury and rehab. I had the only surgery of my career on my wrist [at age 26] and it was one of the reasons I retired.
"There's a lot of doubt …" you just don't know how your body is going to react. Obviously, if anybody can come back, it's Serena. She's done it before and I hope she does it again."
Shriver, who has a good sense of these things, said she thinks we'll see Serena back on the tennis court at some point.
"When she mends all of the multiple aspects of her physical problems, I would be surprised if she didn't make one big comeback," Shriver said. "She's still got a lot of stuff in the tank. I think the challenge to come back from this is in her character, it's right up her alley."
Greg Garber is a senior writer for ESPN.com.