Anthony Kay is on his way to becoming a member of the ever-growing club that includes former Mets prospects who might one day come back to haunt the organization.

The MLB trade deadline was just three days away when the left-handed pitcher learned on Twitter he and fellow hurler Simeon Woods Richardson were being sent from the suddenly surging Mets to the Blue Jays for veteran starter Marcus Stroman.

Stroman has helped the Mets remain in contention, two games out of the second NL wild-card spot.

Meanwhile Kay, like Jarred Kelenic and Justin Dunn — the pair of talented prospects traded last winter to the Mariners for the so-far disappointing Edwin Diaz and Robinson Cano — is impressing with his new organization.

In five starts with Triple-A Buffalo, Kay is 1-1 with a 2.36 ERA. He has allowed just two runs in his last 17 innings, despite walking 5.7 per nine innings, a rate he needs to lower in order to reach the major leagues, where he projects as a back-end starter.

He went 1-3 with a 6.61 ERA in seven games with Triple-A Syracuse while with the Mets.

“Once I got to Buffalo, I wanted to work on getting my curveball more up and down,” he said in a phone interview, referring to a bigger sweep for the pitch. “I think I’ve definitely been able to do that a little bit more than when I was with Syracuse.”

Those numbers have helped soothe his girlfriend’s initial worries over the trade, which they found out about from social media, rather than the Mets, while on their way to the movies.

“She wanted me to stay close to home,” the Long Island native said, but now, “she’s seeing the bigger picture and she’s happier about it.”

Kay is the fifth-ranked prospect in a loaded Blue Jays farm system and likely closer to the major leagues than he would have been with the Mets.

The 2016 first-round pick’s road to the majors has been as unpredictable as the Mets putting together one of the best records in baseball since the All-Star break.

Kay underwent Tommy John surgery a few months after being drafted, missed all of 2017, and had a 4.26 ERA in Single-A ball in his first professional season last year.

He relied on his mid-90s fastball, high-spin-rate curveball and above-average changeup to ascend through the Mets’ system this season and pitch in the 2019 MLB Futures Game.

After dominating Double-A, he hit a wall in Syracuse, and said in July some of his struggles were rooted in the Triple-A baseball, which is the same one being used in the majors. Its tighter construction and lower seams, which MLB commissioner Rob Manfred denies was purposely altered to boost home run production, have turned into a pitcher’s nightmare.

Now, “I’m starting to get more comfortable with it,” said Kay, who grew up a Yankees fan emulating fellow lefty Andy Pettite peering intently over his glove to home plate.

He is beginning to get more accustomed to his new life, as well. While he had dreams of sharing a rotation with fellow Ward Melville High School product and current Mets pitcher Steven Matz, Kay is now a part of an organization boasting some of the best up-and-comers in the game and future superstars in Vladimir Guerrero Jr. and Bo Bichette.

Kay has never been to Canada, but if he continues on this path, it might behoove him to get his passport in order.