Tennis: Jamie Baker and James Ward one step nearer main draw SCOTLAND'S Jamie Baker is through to the second round of Australian Open qualifying following a straight-sets victory over Julio Cesar Campozano. The world No 246 triumphed 6-3, 7-5 over the Ecuadorian in one hour and 32 minutes. Baker put in a solid performance in Melbourne, making just one unforced error against an opponent who, before this contest, was ranked 24 places higher than the 26-year-old from Glasgow. Baker will take on the winner of Matwe Middelkoop against 19th seed Matteo Viola. England's James Ward joined Baker in the second round with a straight-sets win over Boris Pashanski, of Serbia. The British No 4 beat his 30-year-old opponent 6-4, 6-3. Elsewhere, top seed John Isner was knocked out of the Sydney International by fellow American Ryan Harrison but he at least got out on court on a day when injury withdrawals continued to ravage Australian Open warm-up tournaments. World No 5 David Ferrer remained on course for his fourth Auckland Open title, albeit after a tough 6-4, 2-6, 6-3 battle against Taiwan's Lu Yen-hsun in his first outing of the year. Agnieszka Radwanska, the women's top seed in Sydney, set up a semi-final against China's Li Na after both won their quarter-finals in much cooler conditions than the 40°C heat which threatened to suffocate the players on Tuesday. Sydney men's second seed Gilles Simon pulled out before his last-16 match because of a neck injury, while Kei Nishikori and world No 9 Janko Tipsarevic became the second and third players to quit the eight-man Kooyong Classic exhibition event. All are expected to play at Melbourne Park next week. World No 13 Isner, however, was hampered by a bone bruise to his right leg in his 6-4, 6-4 defeat to qualifier Harrison and was left thinking about pulling out of the year's first grand slam. Australian Bernard Tomic confirmed his return to form by riding his improved serve to a 7-6, 6-2 win over fifth-seed Florian Mayer and setting up a quarter-final against defending champion Jarkko Nieminen. Sydney fourth seed Fernando Verdasco was also a loser, 6-3 6-3 to Denis Istomin, while sixth seed Radek Stepanek withdrew injured after four points of his match. Simon's withdrawal followed those of compatriots Jo-Wilfried Tsonga and Richard Gasquet, who pulled out because of a hamstring injury and for "personal reasons" respectively. Former US Open champion Juan Martin Del Potro knows all about injury setbacks but the Argentine world No 7 got his 2013 season under way at Kooyong with a 6-4, 3-6, 7-6 round robin win over Paul-Henri Mathieu. Japan's Nishikori, the world No 18, was forced to pull out with a knee injury, while Tipsarevic was a set down to Marcos Baghdatis when he retired with a wrist injury. There was better news on the weather front in Sydney with temperatures of around 25°C at the Olympic Tennis Centre. World No 4 Radwanska joked that it was "freezing" compared to the previous day's heat after she stormed past Roberta Vinci of Italy 6-4 7-5 and into the semi-finals. Li joined her after beating American qualifier Madison Keys 4-6 7-6 6-2. Slovakian Dominika Cibulkova earlier upset third seed Sara Errani 6-2 6-1 to reach the last four where she will meet second seed Angelique Kerber, who beat Svetlana Kuznetsova 6-3 7-5 in their quarter-final.