NEW YORK — American tennis player Reilly Opelka was fined $10,000 for carrying an unapproved bag onto the court for his second-round match Thursday at the US Open.

It is the largest fine of the tournament, and after Opelka’s 7-6 (5), 6-3, 6-4 victory over Nikoloz Basilashvili Saturday night, he responded to the discipline.

“I mean, what a joke on the US Open to do that. 10K for a pink bag? Come on,” Opelka said after advancing to the first Round of 16 in his career at a major.

“The head referee was telling me you should have come in and had this thing measured,” he continued. “The ref just told me, I mean, I actually thought it was a different bag. We had that logo specifically made. We measured. It is too big. It was not the same bag I was using at the French Open. We made the effort to make it smaller. There was a mistake in production, I think, because in Europe with the conversion, with what was allowed.