BRISBANE – Britain’s Andy Murray reached the semi-finals of the Brisbane International with a straight sets victory over Uzbekistan’s Denis Istomin.The top seed beat the 26-year-old 6-4 7-6 (7-3) as he continues his warm up for this month’s Australian Open.US Open champion Murray struggled in his opening three-set win against John Millman but looked more comfortable in his second match of the year. Murray, 25, will play fifth seed Kei Nishikori of Japan on Saturday.Murray won the first of three titles in 2012 in Brisbane, beating Ukraine’s Alexandr Dolgopolov with the loss of just four games.The world number three went on to win gold at the London Olympics and his maiden Grand Slam at the US Open.Murray’s last four opponent, Nishikori, beat Dolgopolov by the same scoreline.The other semi-final will see Grigor Dimitrov take on 2006 Australian Open finalist Marcos Baghdatis after both beat seeded players.Bulgarian Dimitrov served 17 aces on his way to a 6-3 6-2 victory over seventh seed Jurgen Melzer of Austria. Baghdatis of Cyprus beat French third seed Gilles Simon 6-3 6-4.South Africa beat France 2-1 in their Group B Hopman Cup tie in Perth after Jo-Wilfried Tsonga retired with a groin injury in the deciding mixed doubles.