Alexander Zverev's second Citi Open title in a row is merely the latest sign that he is separating himself from the other up-and-coming youngsters in tennis.
That doesn't mean he is sure that guys such as Roger Federer or Rafael Nadal are worrying just yet.
“You've got to ask them. I don't think Roger's too concerned about it,” Zverev said with a smile. “He's somewhere in Switzerland right now, enjoying his milk from his cow.”
Zverev became the first man in nearly a decade to win consecutive titles at Washington's hard-court tuneup for the U.S. Open, overpowering Alex de Minaur 6-2, 6-4 in the final Sunday.
Juan Martin del Potro won the Citi Open in 2008 and...