Seattle Mariners Executive Vice President & General Manager of Baseball Operations Jerry Dipoto announced today that Justin Hollander has been promoted to Assistant General Manager. In addition, Leslie Manning has been promoted to Director of Professional Development and Assistant Director, Player Development.


Ten others in baseball operations also received promotions and new responsibilities.


Justin Hollander had served as Director, Baseball Operations since being hired by the Mariners on September 23, 2016. Justin works closely with Dipoto and VP/Assistant General Manager Jeff Kingston on player procurement, negotiations of Major League contracts, 40-man roster composition and baseball statistical research. Prior to joining Seattle, Justin spent nine seasons in the Los Angeles Angels front office, having served in several different roles in the Angels baseball operations department.


“Justin has made real impact in all aspects of our operations since coming aboard in 2016,” Dipoto said. “This promotion is much deserved and better defines his contributions to the organization. Justin, Jeff and the rest of our Baseball Operations team will continue to collaborate in our ongoing effort to build a championship organization.”


Leslie Manning has spent the past two years as the Mariners Coordinator of Professional Development. She will expand those duties as Director of Professional Development and take on new responsibilities as the Assistant Director of Player Development. Manning, who is bilingual in Spanish and English, has spent the last decade working in baseball at the Major, minor and NCAA Division I levels. She was the Director of Baseball Operations at Santa Clara University in 2016 and 2017, is the founder of NextStep Baseball, and has worked at the MLB Office of the Commissioner in New York, in baseball operations for the Arizona Diamondbacks and for Short-Season and High-A affiliates for the Colorado Rockies and Boston Red Sox. She is the 2011 New York Penn League Executive of the Year.


“Over the past two years, Leslie has earned the trust and respect of our staff and players” said Andy McKay, the Mariners Director of Player Development. “Her ability to create clarity and bring accountability to our process is unparalleled. In her new position, she will have a wider reach and will ensure that our actions meet our words throughout the entire organization.”


Additional Promotions announced today are:


  • Emanuel Sifuentes has been promoted to Player Personnel Manager from Coordinator, Video Advanced Scouting.
  • Joel Firman has been promoted to Manager, Analytics from Analyst.
  • Tim Stanton has been promoted to Manager, Baseball Operations from Coordinator, Amateur Scouting.
  • David Hesslink has been promoted to Coordinator, Baseball Operations from Assistant, Baseball Operations.
  • Andrew Herrera has been promoted to Coordinator of Scouting from Assistant, Baseball Operations.
  • Ty Bowman has been promoted to Asst. Coordinator of Scouting from Midwest area scout.
  • Frankie Piliere has been promoted to Coordinator of Advanced Scouting from the Mariners Scout Development Program.
  • Skylar Shibayama has been promoted to Asst. Advanced Scout from analytics intern.
  • Ben Aronow has been promoted to Analyst from analytics intern.
  • Forrest Diamond has been promoted to Analyst from analytics intern.