Japanese tennis star Kei Nishikori has enlisted the help of Michael Chang as he looks to break into the top 10 in 2014. Chang will join Nishikori's coaching staff for 17-20 weeks, Nishikori's management team announced on Wednesday. The 41-year-old American will act as an advisory coach to the 17th-ranked Nishikori, with full-time coach Dante Bottini remaining in his current role. Nishikori has been training with Chang for the last two weeks in California. More...