Big hair, big forehands and big opinions have ensured the Williams sisters are the most talked about players at the Australian Open, while Lleyton Hewitt is facing calls online to hang up his racket.

Serena Williams, the world No.3, and sister Venus, the world No.26, have topped IBM’s Social Media Leaderboard so far at this year’s Open – a chart tracking and analysing Twitter conversations about all the players.

The American siblings have had tens of thousands of tweets sent about them since Monday and the sentiment contained within those short messages has been mostly positive.

About 80 per cent of the tweets about Serena were rated as `positive’ as were about 94 per cent for Venus, according to IBM’s data.

Key to the Williams sisters’ popularity on social media is the fact both are active on Twitter and engage with fans.

Serena has more than three million followers, while Venus has 900,000.

Their eye-catching outfits, hairstyles and enduring tennis skills have also played a major role in their popularity online and ensure they continue to be talked about.

World No.1 Novak Djokovic was the third most talked about player and the highest ranking among the men so far at the Australian Open, followed closely by Scottish ace Andy Murray.

Australia’s top player Bernard Tomic has not fared so well on IBM’s social media leaderboard.

He’s not featured in the top 10 so far this tournament, though that is likely to change on Tuesday night as he plays his first match against Argentine Leonardo Mayer.

Meanwhile Hewitt, who crashed out of the first round on Monday night, is facing calls to quit.

“Lleyton Hewitt should just retire!” one user wrote on Tuesday.

Others expressed support for the South Australian and urged him to continue.