Serena Williams admits over-confidence could be the biggest obstacle to her bid to win a fourth Wimbledon singles title in Saturday’s final against Vera Zvonareva.

Williams has swept to the final in such dominant fashion that few outside of Zvonareva’s family and friends expect anything other than a convincing victory for the defending champion.

The American top seed has yet to drop a set at this year’s Championships and has sent down a total of 80 aces as she bludgeoned opponents into submission with her ferocious serve.