Jonah Tong introduced himself around the Mets clubhouse, to the media and to the extended organizational family at Citi Field on Thursday, a smiling, baby-faced, extroverted 22-year-old from Canada happy to be here and breathing it all in.

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“Talking to him — he’s a kid,” were the words of Carlos Mendoza.

That kind, thoughtful and youthful spirit will not be who takes the mound Friday for his major league debut.

The Mets instead will give the ball to J.T., a kind of alter ego who might not be as nasty as his stuff but is certainly not as joyful as his soul.