Reality of the health situation Serena Williams is in

The health and injury problems to Serena Williams have once again shown that an athlete's health should never be taken for granted.

Serena Williams's comments last week on her life-threatening medical emergencies, which included blood clots, a pulmonary embolism and a haematoma the size of "a grapefruit", prompt reveries along two tangents.

The first is the realisation that the nine-month absence of one of the leading personalities on the women's tour almost certainly will extend a full year - and could even end her career at age 29.

Her last official match was at Wimbledon, where she won her 13th grand slam title on July 3 when she routed Vera Zvonareva in the women's final.

Only four days later she reportedly stepped on broken glass in a Munich restaurant, suffering a cut that required 18 stitches to close. She managed to play an exhibition match in Brussels a day later, losing to Kim Clijsters before 35,681 fans - the largest crowd to see a tennis match.

She had surgery on the wound in October, and the year ended without a return to the court.

Her situation turned dire last month. She had been diagnosed with blood clots in her leg. One clot travelled to her lung, creating the embolism. More blood gathered on her stomach, the "grapefruit" she referred to. She called it the "scariest moment in my life".

She said she still had clots on her lung but expects them to dissolve. On Twitter she told fans: "I am better each day."

Meanwhile, the top WTA players, Clijsters and Jelena Jankovic, wished Williams a speedy recovery and conceded that her absence diminished the women's game. Clijsters also spoke of her concern that long plane flights can cause blood clots in legs. "The toughest part for us is flying all over. It's very scary. It's very serious."

The second tangent from Williams's health scare is the realisation that fans often now assume that top athletes can be felled only by injury. Those assumptions were not made just a century ago, before the advent of antibiotics.

The British footballers George Allan and Thomas Bradshaw died from tuberculosis while in their 20s.

Jack Jones died from scarlet fever and Jeff Hall from polio.

Among baseball players, Tiny Bonham and Jake Daubert succumbed to a ruptured appendix, Addie Joss to meningitis, Doc Powers to gangrene.

Serena Williams's health issues are a reminder that the careers of athletes can be ended by events far more dire than tendinitis, sprains or boredom.