The No. 1 overall pick in the 2023 NBA Draft was speaking to reporters ahead of the Spurs' matchup against New York ... when he was asked about playing in the Mecca for the first time.

The 19-year-old certainly seemed unenthused with his response ... saying, "It’s not as big as I expected, but still the vibe is here."

Wemby's remark was shared all over social media ... and of course, the Knicks fans didn't take it well.

"He gone learn todayyyyyy 😂😂😂😂!" one Knicks fan said on Instagram ... while another hilariously added, "Oh I'll show you big, Mr. Wobblymama."

"That’s cause you big as hell ... don’t disrespect the Garden," a Knicks backer echoed. "You see how we treat Trae Young when he come here 😂😂."

Of course, that user is referring to the hell Knicks fans put the Atlanta Hawks star through over the years -- chanting "f*** Trae Young" and more ever since he became the current villain for the entire organization.

Knicks fans AND players are prepared for Wemby ... especially Mitchell Robinson, who said earlier this week he knows how to handle a 7'4" guy like Victor.

"I'm not really worried about the tallness s***," the 7-foot center said. "Just go out there and play hard."

And Mitch knows he can count on Knicks fans to be loud as hell during tonight's game after Wemby's "diss."

FYI -- MSG seats 19,500 people ... and yeah, it's gonna sound like that in a few hours.