A splendid time seems guaranteed for all at the celebrity-rich, cast-of-hundreds U.S. Open. Except some days, amid all the jumping through hoops of fire and somersaulting across the big stage by the world’s tennis elite, circumstances prevent a leading character’s star turn.

Such was the case Wednesday, when defending champion and top seed Novak Djokovic did not appear for his scheduled afternoon performance. Through no fault of his own, Djokovic — unseen — proceeded to Thursday’s third round via a walkover when dangerous young Czech Jiri Vesely defaulted because of forearm inflammation.

The absence of the Djokovic match caused No. 10 seed Gael Monfils vs. Jan Satral to be moved from Court 17 to Arthur Ashe Stadium, and No. 7 Maric Cilic vs. Sergiy Stakhovsky from Court 5 to Court 17. Both Monfils and Cilic won in straight sets.

This year’s Open already was missing familiar headliners Roger Federer (rehabbing a surgically repaired knee), Maria Sharapova (serving a doping suspension), Victoria Azarenka (pregnancy) and Flavia Pennetta (just retired) — all major tournament champions.

So, naturally, there has been something of a spectator-letdown factor, with which Vesely certainly can identify.

“I’m very disappointed right now,” said Vesely, at 23 ranked 49th in the world and enjoying his best year on the pro circuit. “I was looking forward to that match. It’s big for me, or every young player, exciting to play on a big court, the biggest court in our tour and playing against Novak, the No. 1 player in the world.”

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Vesely had played in Arthur Ashe Stadium once — a first-round, straight-sets loss to Stan Wawrinka. But that was in 2014, when Vesely was the reigning Australian Open champ and Vesely was a 21-year-old who not yet had broken into the top 70 rankings.

Just five months ago, Vesely defeated Djokovic in Monte Carlo, and in June he advanced to the fourth round at Wimbledon, his deepest run in a Grand Slam event, clearly boosting his expectations for Flushing Meadows.

But a week ago, at the Open tune-up tournament in Winston-Salem, Vesely developed the inflammation in his left forearm — he is lefthanded — forcing him to withdraw in the midst of his quarterfinal match there. “The muscles started to pinch the nerve, so obviously I didn’t feel much control in my hand,” he said.

He didn’t practice for four days, then aggravated the injury during his first-round Open match Monday while rebounding from a two-set deficit for a five-set victory over Indian qualifier Saketch Myneni. He was unable to practice on Tuesday and realized early Wednesday that “it’s really not good for me to play” against Djokovic.

So, the marquee production had to be skipped and, in the end, Vesely wasn’t the only loser.