The door is open, if you look at the rankings, you have a lot of players positioned to make a big breakthrough, i believe there will be a changing of the guard this year. Whether it's Zverev, or one of the others like Khachanov or Tsitsipas, you're going to see them do something big.

John McEnroe

John Patrick McEnroe, Jr. (born February 16, 1959) is an American former World No. 1 professional tennis player. McEnroe won seven Grand Slam singles titles-three at Wimbledon and four at the US Open-nine Grand Slam men's doubles titles, and one Grand Slam mixed doubles title. He is remembered for his shot-making artistry and superb volleying; for his famous rivalries with Bjern Borg, Jimmy Connors, and Ivan Lendl; for his confrontational on-court behavior, which frequently landed him in trouble with umpires and tennis authorities; and for the catchphrase "You cannot be serious!" directed toward an umpire during a match at Wimbledon in 1981. He was inducted into the International Tennis Hall of Fame in 1999

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