The Austrian forward joined the Lions towards the end of last week on a short-term deal and made his debut as a second-half substitute in Saturday's goalless draw with Charlton.
"Big Stefan will make a difference for us," said Den boss Holloway.
"In the last couple of weeks we've gone 1-0 down in two games and the other team have sat back and we couldn't break them down.
"With Stefan up there teams won't be able to drop off. We'll be more difficult to defend against."
Holloway also handed a full debut to 17-year-old academy product Fred Onyedinma against the Addicks.
He added: "Young Fred had a great game. He was terrific, he really was.
"The problem was we probably didn't give him the ball enough because he has loads of tricks in his locker.
"I'm not afraid to select any of the younger ones because their hunger is terrific."