McEnroe added: “And maybe that’s one thing I wish I had grabbed on to a little bit earlier. Because I do think it’s really paying off, not just for us but for American tennis in general.”

During McEnroe’s tenure, the number of top-ranked men has ebbed. In 2008, eight American men were in the top 100 of the world rankings, and Andy Roddick was still in the top 10. Three others were in the top 50. Now, only 15th-ranked John Isner, who was eliminated Saturday in the third round of the Open, is in the top 50, and only six Americans are in the top 100 over all.

On the women’s side, the story is different. Led by Williams, the number of American women in the top 100 has steadily increased, from five in 2008 to a dozen in the current rankings. The number in the top 50 over those years has doubled, to eight.

But Williams, who with her sister Venus learned the game from their father, is not considered a product of the U.S.T.A. development system, and many have asked whether expectations are too great to believe a national high performance center could hone the next Williams.

“Obviously, we’re doing pretty well on the women’s side,” McEnroe said. “We’ve got a lot of work to do on the men’s side at the top, but I think we have a great group of youngsters coming up. Now I think we’re all very optimistic about the future for them. There’s a lot of tentacles that go into this job. Certainly more than I realized going forward, and that’s why having a great team in place, and some of them here, to me is probably the most important, having the right people in place to do the job.”

As head of player development, McEnroe was paid about $875,000 in 2012, according to the U.S.T.A.’s financial forms, and more than $1 million in each of the three previous years.

Critics of his role in player development have pointed to his numerous television appearances and have questioned how he could focus on being an analyst while also earning a seven-figure paycheck from the U.S.T.A.