Former fourth-ranked Nicolas Kiefer of Germany has announced his immediate retirement from professional tennis. The 33-year-old Kiefer said on his website Thursday that he wants to spend more time with daughter Mabelle Emilienne, who was born in August. Kiefer, who rose as high as No. 4 in the world rankings in 2000, won six tournaments and reached the semifinals of the Australian Open in 2006. More...