CLEVELAND — When he first learned that the Mets were trying to trade him to the Seattle Mariners last fall, Jarred Kelenic was not even sure it was legal. Hadn’t the Mets just chosen him in the first round of the draft that summer?

Kelenic was at dinner then with teammates at an off-season training camp in Port St. Lucie, Fla. He dismissed the rumor, but it resurfaced a few days later, after he had gone home to Wisconsin.

“My mom called me and she was like, ‘This is probably going to happen,’” Kelenic said on Sunday. “I was like: ‘Mom, this doesn’t happen to first-year guys. It just doesn’t happen.’”

But it did, officially, on Dec. 3, with a deal that could haunt the Mets for years. Brodie Van Wagenen, the former agent who had just become the Mets’ general manager, packaged Kelenic and a previous first-round pick, pitcher Justin Dunn, as part of a seven-player deal for closer Edwin Diaz and second baseman Robinson Cano.