The sultry days of late summer are laid-back, but in tennis the operative concept is laid-up. That's just part of the reason this hard-court season could be the most unpredictable in recent memory. Stan Wawrinka, the defending US Open champion, announced Friday that he's finished for the year because of a knee problem. "After sitting together with my team and considering all options, I have made the very difficult decision to end my 2017 season," the No. 4-ranked Wawrinka told the ATP media department. "I need to undergo medical intervention on my knee." Read more http://www.espn.com/tennis/story/_/...ria-sharapova-injuries-more-proof-safe-summer
