Serena Williams admits she has plenty of work to do to ensure her game is ready for clay ahead of the start of the French Open next month.

The American was pushed all the way by Italy’s Sara Errani during their Fed Cup duel at the weekend, eventually triumphing 4-6 7-6 6-3.

However, she then struggled in the doubles as herself and Alison Riske were beaten in straight sets by Errani and Flavia Pennetta as the USA went down 3-2 in the tie to relegate them to World Group II.

Williams now has bigger things to think about, most notably the upcoming French Open for which she is currently the 3.50 favourite to win ahead of her great rival Maria Sharapova who is priced at 5.00.

After cruising through to victory at the Australian Open it has been suggested that the 33-year-old could win all four Grand Slams in 2014.

Roland Garros has traditionally been her weakest of the major venues though, with just two of her 19 crowns coming in the French capital.

The world number one admits her form over the weekend was nowhere near good enough and concedes she faces plenty of hours on the practice court to get herself ready to compete at the highest level on the red dirt.

“I’m totally not as ready for the clay-court season as I thought I was,” she said. “Now I’m in the mindset of ‘you know what, I’m not on hard court.’ I’m playing like I’m on hard court and I’m not.

“So I have to play and be ready to hit a thousand shots if necessary.”