Novak Djokovic won his 15th straight match and Roger Federer avenged last week's loss to Juan Martin del Potro, setting up a semifinal match between the two at the Paris Masters. Djokovic beat Stanislas Wawrinka of Switzerland 6-1, 6-4, while Federer defeated Del Potro 6-3, 4-6, 6-3 Friday. ''Coming to the net is one of the improvements that I had recently,'' Djokovic said. I had to work and put in many, many hours on the practice court that you guys don't see.'' Wawrinka lost five-setters against Djokovic at the Australian Open and the U.S. Open this year. More...