Britain's Andy Murray downed Gilles Simon in straight sets to reach the Masters Cup semi-finals on Wednesday as Andy Roddick joined Rafael Nadal on the injury list. Murray overcame some dogged resistance to win the first set and ran away with the second to take it 6-4, 6-2 and follow third-ranked Novak Djokovic into the last four. "Although he did come back I was always ahead in the first set," Murray said. "In the second set I dictated a lot of the points, moved him around a lot and didn't make too many errors." Murray beat Simon in Hamburg and in the Madrid Masters final this year, both in straight sets, and victory looked assured as he raced to a 4-0 lead in the first set.