Serena Williams: 'Venus's health is more important than tennis'

Serena Williams has insisted that the health of sister Venus is more important than playing tennis.

Venus withdrew from the 2011 US Open on Wednesday after being diagnosed with the autoimmune disorder Sjögren's syndrome, a revelation which came just months after Serena suffered a pulmonary embolism and hematoma.

Talking to People, 29-year-old Serena revealed that Venus is attempting to remain positive despite the illness, which causes severe fatigue and joint pain.

"She's doing better. It's a day at a time kind of a thing. Her spirits are good, however," Serena said.

"Tennis is great, but [Venus's illness] puts everything in perspective. I love playing tennis and I love the battle, but I realise that life is so precious and it isn't all about tennis."

Serena admitted last year that she wanted to be like Venus while the pair were growing up and was jealous of her figure.