Australia\'s Sam Willoughby and defending Olympic champion Maris Strombergs of Latvia battled their way through a series of crash-marred races to qualify for the men\'s BMX semi-finals Thursday. The two best placed riders from each eight-man heat after three races qualified directly for the semi-finals. Willoughby, the reigning world champion, finished only third in his heat after three races meaning he had to complete two more races before making the last 16. After qualifying, the Australian gold medal hope said: \"A couple of mistakes early kind of cost me, but I\'m still pretty safe so I\'ll keep the energy for tomorrow. \"It\'s a good little learning curve for me and I\'ll be better for it tomorrow.\" Given the performances of some of their rivals, Willoughby and Strombergs look to be facing some stiff competition in Friday\'s semi-finals. Dutchman Raymon Van der Biezen, whose team had built a replica of the Olympic track to optimise their medal chances, finished first in all three of his races to qualify directly. \"I did what I had to do,\" said the Dutchman, who had secured the gate starting position number one in the seeding run Wednesday and kept it for his next two races. \"I had the start on the inside, which is a slight advantage and I used it well.\" Connor Fields did likewise, while Britain\'s Liam Phillips finished second behind the American in each of their three races to qualify directly. Phillips was only too happy to avoid the crashes which ended several riders\' bids for a medal. \"I\'ve been on the receiving end of a lot of crashes but you try and block it out,\" said the 23-year-old, who failed to get past the quarter-final stage in Beijing. \"You focus on your own stuff and take one lap at a time. That is part of BMXing.\" In heat three New Zealand\'s Marc Willers and Frenchman Joris Daudet, the silver medal winner at the world championships, also went straight through, as did Dutchman Twan van Gendt and Strombergs from heat four. Strombergs said he \"wasn\'t too satisfied about my first and second races\" and doesn\'t expect it to get any easier. \"I never thought it was going to be that hard to come in as Olympic champion. It\'s a lot of pressure and when you start thinking about it, it\'s really hard to focus on yourself and what you really want to go out there and do.\" American David Herman, Roger Rinderknecht of Switzerland, Willoughby and Colombia\'s Zabala Oquendo of Colombia also qualified after completing two extra races each.