His years of trying to win over amateurs who he believed could turn into major leaguers have informed his approach. Todd Frazier, the Mets’ third baseman, goes back with Van Wagenen the furthest. He recalled first meeting Van Wagenen in his parents’ living room in Toms River, N.J., when Frazier was a junior at Rutgers. Charlie and Joan Frazier had raised two professional baseball players by the time they took the measure of Van Wagenen as Todd’s potential agent. Van Wagenen ended up representing him for 12 seasons.

“Your agent becomes family if you’re with him that long,” Frazier said. “He is whip smart and always has been. He’s someone I respect and always will.”

As an advocate, Van Wagenen’s voice was always heard above the din. In 2018, when the free-agent market slowed nearly to a halt, Van Wagenen, who was an agent for 18 years, charged that owners were colluding to suppress player salaries.

DeGrom — one of eight Mets, including three of the five starting pitchers, on the roster whom Van Wagenen once represented — was in the middle of a historic season last year when Van Wagenen publicly suggested at the All-Star Game that the Mets should trade his client if they were not willing to extend him. Three months later, Van Wagenen informed deGrom that he no longer represented him. He was his boss.

“I’m hoping my understanding of the player mind-set will be an advantage when I’m communicating internally here,” Van Wagenen said.

After he crossed over to management, however, an extension for deGrom was one of the few topics on which Van Wagenen remained silent this spring, highlighting the delicacy of his pivot from his past profession. Tony Clark, the head of the players’ union, expressed concern regarding Van Wagenen’s switch. While the Mets billed Van Wagenen as an unconventional hire, the agent Scott Boras, his formal rival, noted ethical worries about the inside information Van Wagenen could bring to coming negotiations involving his former clients.