The 20-year-old forward (6-foot, 205 pounds) gained a better understanding of that while skating with Devils forward Jesper Bratt and skills coaches in Sweden in early July.
"I'm just trying to take some stuff out of his routine and use in mine," Holtz said. "It was nice to be around him every day, see how he does it. He's constantly working and to see how he does it, with his skating and everything, is important because he's such a good player."
Holtz, the No. 7 pick in the 2020 NHL Draft, took the advice given by Devils management this offseason to heart. He appeared more physically fit and trim during development camp from July 11-15.
"I think maybe I lost some (bad) weight but gained some muscles," said Holtz, who was listed at 195 pounds last season. "That's what I wanted to do. I have a lot more weeks to work on that before training camp as well."
Devils assistant general manager Dan MacKinnon is glad Holtz listened.
"At our exit meeting with him, we told him elite-level conditioning is going to give you the best opportunity to push for a regular NHL spot," MacKinnon said. "It's not his shot, it's not his creativity, it's being in the best shape of your life.
"That's one of the reasons we brought him back from Sweden for development camp. We wanted to make sure everything was on track, and he looks great."
Holtz played for Utica in the American Hockey League last season, finishing fourth on the Comets with 51 points (26 goals, 25 assists) and second with seven power-play goals in 52 games. He had three points (one goal, two assists) in five Calder Cup Playoff games.
"The Devils coaching staff wants me to be faster and I want to be fast," Holtz said. "I want to be stronger. I want to make an impact. They want to see that I'm comfortable at this level and play my game.
"I also want to be that guy on the left side on the power play that's that hammer for one-timers."