Daniel Murphy’s return to Citi Field Tuesday night as a member of the NL East rival Nationals for the first time since he inspired the Mets’ run to the National League pennant last season had all the trappings of a graduation ceremony.

Murphy accepted his NL championship ring from general manager Sandy Alderson, delivered a valedictory news conference, enjoyed a video tribute and accepted two standing ovations from Mets fans after the video and before his first at-bat leading off the second inning. The .400 hitter then fouled out, giving Mets fans another reason to cheer.

Coming off last season’s emotional thrill ride to the World Series, these rituals were necessary for Murphy and for Mets fans to cut ties forged over his 10 years in the organization, including the past seven in New York. It worked because he was booed before his second at-bat, a two-out bloop single.

The experience of going to the visitor’s clubhouse was different, Murphy admitted. “I’ve only been over there once,” he said. “It was for a fantasy football draft that David (Wright) had a few years ago. But man, a lot of great memories in here, a lot of great memories in this stadium with the Mets organization. I thought they treated me as fairly and first-class as they possibly could.”

That continued Tuesday night when Alderson presented the MVP of the NLCS his ring plus a pendant for his wife. “I made it clear to him that, without his substantial contribution, none of us would be wearing that ring today,” Alderson said.

True, but Alderson’s refusal during the offseason to engage in meaningful free-agent negotiations made it clear the organization could live without him. So, Murphy accepted the Nationals offer of $37.5 million over three years.

“We had an approach that we thought we should pursue,” Alderson said. “I think it’s turned out well for him, and it’s turned out well for us.”

The finality of the situation hit Murphy the first time the Nationals faced the Mets in spring training. “I saw the orange and blue on the other side and I was wearing the red, it kind of put aside what had happened in New York,” Murphy said. “That’s not going to wash off easy . . . but the red gets more comfortable every day.”

Murphy carried his postseason success south to D.C., averaging .400 through his first 37 games with five home runs and 23 RBI while compiling a 1.062 OPS and an MLB-best 56 hits and 19 multi-hit games.

“As far as the postseason last year, I just felt like the game was moving slower . . . and I was able to execute all the plans I was trying to against pitchers. That’s kind of where I’m at right now.”

Murphy thanked the Mets for the “classy” video tribute, but he added, “Once that ends and 7:10 starts, it’s prison rules out there, a division opponent.”

The only thing missing from Murphy’s rite of passage Tuesday night was his familiar walk-up music by the Dropkick Murphys, which would have been supremely appropriate because the Mets and their fans now count him among the departed.