World number one Roger Federer fought out a testing three-set victory over Nikolay Davydenko of Russia in the men's singles tennis on Monday.
The Wimbledon champion and gold medal favourite claimed a 6-3 5-7 6-1 win in one hour and 45 minutes.
Earlier, Australia's Mark Philippoussis crashed out after losing to Belgium's Olivier Rochus 6-3 0-6 1-6.
And third seed Carlos Moya of Spain saved three match points to beat Sweden's Thomas Enqvist.
Moya came through 7-6 (9-7) 6-7 (8-10) 9-7 and will now face Rochus for a place in the last 16.
Meanwhile Federer will face Tomas Berdych of the Czech Republic in the second round.
There was yet another upset when 12th seed Paradorn Srichaphan was a surprise 6-2 6-3 loser against Joachim Johansson of Sweden.
Elsewhere Americans Mardy Fish and Andy Roddick lost to India's Mahesh Bhupathi and Leander Paes in the doubles.