Popper will take over the team's goaltenders for Michael Garman, who was promoted from associate head coach to general manager in July. Whitmore's primary responsibility will be on the offensive side of the puck.
Associate head coach Matt Deschamps will return for his third season behind the Steel bench alongside head coach Brock Sheahan.
Popper and Whitmore each join the Steel from the NCAA Division I level.
Popper, 29, spent the past three seasons with Minnesota (2018-21) men's and women's teams. Last season, he worked with Carolina Hurricanes prospect Jack Lafontaine, who won the Mike Richter Award as the NCAA's best goalie. Prior to Minnesota, Popper coached goalies for Ohio State's women's team during the 2016-17 season.
Whitmore, 36, spent this past season as an assistant for Mercyhurst men's team after holding the same role for Division III Bowdoin College women's team for two seasons. He played in the USHL for Waterloo and Lincoln then had a standout career at Bowling Green. He played parts of 11 seasons professionally, including a two-game stint with the Buffalo Sabres in 2011 and 369 AHL games, before stops in Germany, Austria, and the ECHL.
Garman on Popper
“He has a holistic approach and brings a unique and diverse skill set that will continue to enhance our player and goalie development. Popper will contribute to all areas of coaching while primarily developing our goalies."
Garman on Whitmore
"He brings invaluable mentorship to our players from his impressive playing career - over 500 pro games, including NHL, AHL, ECHL, and several years in top European leagues. In addition to coaching, Derek has over 10 years of skill development experience and will also assist in individual player development."