NEW YORK — Mike Piazza glanced high toward his No. 31 that will forever hang over Citi Field and urged New York Mets fans, hoping to find faith in the most trying moments, to do the same.

“So every time these guys are down and you need a little bit of inspiration, just give a little peek up there to ol’ Mikey,” he told an adoring crowd Saturday night.

The Mets retired Piazza’s number in a half-hour ceremony before playing Colorado, six days after he was inducted into the Hall of Fame in Cooperstown.

Speaking at a podium in center field, the 12-time All-Star catcher had to catch himself once, when the emotions started to well up inside him.

“You’ve given me an honor that no man deserves and no player deserves,” Piazza said.

The tribute included his parents, family members, former teammates, friends and a lot of chanting and cheering. He ended his 6-minute speech with a shout of “Let’s go, Mets!”

The 47-year-old Piazza became the fourth Mets person to have his jersey retired by the team, joining pitcher Tom Seaver and managers Casey Stengel and Gil Hodges.

Piazza’s number now hangs in a big circle on the facade above the upper deck in left field.

“That means I will always be with you,” he said, adding that when the Mets are struggling, “know that I’m back home watching you guys on TV, saying a lot of prayers — praying for the Mets. And listening on the radio.”