Tightening up the pace of play, rolling out an expanded instant replay system, initiating a broad-based effort to engage youth, retooling quarterly owners meetings, implementing new recommendations for ballpark safety netting, and preparing for this year’s labor negotiations with the MLB Players Association — it made for a full year for Marinak, for years a key adviser to Manfred and a Forty Under 40 honoree in 2015, as well.

But as Manfred began as commissioner at the start of last year, Marinak expanded his own role in the new MLB leadership regime and became a critical cog in articulating the commissioner’s early agenda. In particular, Marinak played a key role in the development and rollout of the new instant replay and pace-of-play provisions, as well as Play Ball, a joint initiative with USA Baseball to boost youth baseball participation, even outside organized leagues.

Manfred’s early tenure has also been marked by a substantial increase in the transparency and contact between individual clubs and the MLB league office, and Marinak has been a central fixture in that effort, as well, meeting personally with each of the 30 clubs last year to help develop management’s overall platform in the collective-bargaining talks with the players. As a result, Marinak has deepened his own ties to team owners and executives.

“There have been a lot of increased opportunities to work closely with the clubs,” said Marinak, who’s been at MLB since 2008. “One of Rob’s key goals has been to have the increased level of dialogue with teams, and it’s been very fulfilling to help meet that vision of transparency that he has. It’s made us a stronger league and a stronger sport because of it.”

— Eric Fisher