Maybe it was the court after all.

World No. 4 Holger Rune was defeated in a shocking upset at the hands of the No. 63 seed Roberto Carballes Baena at the U.S. Open on Monday, just days after the 20-year-old voiced his complaints about his suboptimal court placement.

“In case you can[‘t] find court 5, this is where I play my first match Monday followed by 11:00,” Rune, who is riding a career-high singles ranking, snarkily wrote on X on Saturday after the draw was revealed.

Court 5 is placed just outside Arthur Ashe Stadium at the Billie Jean King National Tennis Center — not the place you would usually expect to find one of the top five seeds in the world.

One way or another, Rune was not comfortable on Court 5 on Monday, when Carballes Baena earned a 6-3, 4-6, 6-3, 6-2 victory to down the young rising star, who boasted a 37-15 record and one title on tour this year before arriving in New York.

It was the Dane’s fourth-set double fault that gave Carballes Baena a 4-2 lead in the final set and spelled the end for Rune.

Rune also lost eight straight points during the third set and committed 41 errors on the day, resulting in his untimely exit.

The U.S. Open is statistically the worst major for Rune, who lost in the first round of 2021 to Novak Djokovic and was downed in the third round last year to Cameron Norrie.

The Danish star doubled down on his court placement complaints when speaking to reporters before his match, telling a Danish TV station he agreed that it was “disrespectful.”

“I completely agree,” Rune said. “It is two ATP managers/supervisors who always give me the worst courts. So that’s how it is.”

“But I don’t mind complaining about it. I have a tournament to win and I have to be focused. I have to do my best, no matter what court I’m on.”