When the United States Open begins Monday, the best tennis players in the world will unleash overpowering serves, crackling forehands and paralyzing returns. Then they will retreat behind the baseline and use a no-less-visible weapon of choice: a 100 percent cotton official tournament towel.

In the men’s game in particular, tennis and towels are much more in tandem now than the faded tactic of serve-and-volley. For various reasons, sometimes including actually drying off, players have increasingly been, as they say, going to the towel.

As Roger Federer recently described it, “For some players, like a security blanket.”

Beyond noticeable, it has made some people irritable. At Wimbledon, while commenting for television, John McEnroe wondered why players needed to towel off between so many points under conditions that were typically cool. At the same tournament, John Newcombe, the No. 1 player in 1967 and who is now 70, summed up the incredulity of his generation by observing: “Can we stop the towel, please? Hit one ball, towel.”

At a time when several sports — Major League Baseball foremost among them — are grappling with ways to reduce the duration of games to accommodate shorter attention spans and more television choices, quantifying how rampant towel use affects the length of tennis matches is difficult because the matches differ wildly in terms of competitiveness. But people watching know when one is dragging on, seemingly forever.