HOUSTON — After months of anticipation, the Mets finally got to see Juan Soto in action for real on Thursday.

On Opening Day, he was there, with runners on base, two outs, and the Mets behind by two runs against the Astros’ pitcher Josh Hader.

Clay Holmes described the tense atmosphere in the dugout during the ninth inning of the Mets’ 3-1 defeat to Houston at Daikin Park.

He shared, “The energy was high, everyone was urging to get Juan to bat and see the outcome. We have confidence in him, and most of the time, we believe in his abilities.”

This time, though, Soto came up short.

Hader started Soto off with a sinker that missed high, as did the second pitch of the at-bat, a slider that ended up low.

With the count 2-0, Soto took another sinker outside the zone, up and away.

At that point, Soto took another slider, this one for a strike, right in the heart of the plate.

And then Soto had what Carlos Mendoza said was Soto’s best swing of the at-bat, a sinker that he fouled off.

“He put his ‘A’ swing there,” Mendoza said. “He just missed it.”

Soto then circled the batter’s box before the next pitch, when he got a 3-2 slider that ended up well off the plate.

Soto offered a very un-Soto-like swing and the weak offering wasn’t close, as Soto’s first game with the Mets ended in disappointment.

“I was expecting to be up in that moment, that situation,’’ Soto said of the opportunity to potentially tie the game with an extra-base hit. “[Hader] let the ball go on that last pitch and got me on that one. It was a pretty good pitch down and away.”

Soto acknowledged he didn’t think a slider was coming.

“I was expecting his best pitch,” Soto said. “His best pitch is a fastball. I was sitting on a fastball.”

“That was a pretty nasty pitch by Hader,’’ Mendoza said of the final slider. “He got him this time.”

And Soto insisted he would have been fine drawing a walk to load the bases for Pete Alonso, something he would have done last year, with Aaron Judge behind him.

“For me, I don’t mind taking a walk right there,” Soto said. “Pete’s behind me, a really good power hitter. I think we have a good chance right there, lefty [versus] righty. He just got me in that situation.”