Novak Djokovic has pulled out of the Monte Carlo Masters because of a knee injury. The second-ranked Djokovic said in a statement that his withdrawal is a "tough blow" because the Monte Carlo Masters is "his favorite tournament." Djokovic is undefeated so far this year with a 24-0 record. The Australian Open winner didn't say how long he will be sidelined. Read more: http://sports.espn.go.com/sports/tennis/news/story?id=6309490
