WASHINGTON — Zion Williamson, Duke’s dominant freshman, finally looked lost.

There was less than a second left on the game clock, and Williamson’s top-seeded Blue Devils held a 75-73 lead over fourth-seeded Virginia Tech in a round-of-16 showdown in the N.C.A.A. men’s basketball tournament.

Virginia Tech point guard Justin Robinson prepared to inbound the ball from the baseline, and his teammate Ahmed Hill sprinted from the paint toward the corner before curling back to the rim. Guarding Hill, Williamson took one step too far, trailing the Hokie as Robinson led Hill to the rim with a lob pass.

“I’m not going to even lie to you, when he caught it, I said, ‘Oh, we’re about to go to overtime,’” Williamson said. “I don’t know what happened. It just kind of went our way.”

The ball did not go in. Duke won.

When asked how his team usually defends that play, Duke Coach Mike Krzyzewski said, “Better.”