Grujic joined the German outfit on loan in the summer but suffered an ankle injury earlier in the season. He made his return in Sunday's 3-1 win at Nurnberg and impressed his temporary boss.
“This is the first time in my life when I didn't have to settle with the middle shelf of the supermarket, instead I was able reach the top shelf," Dardai told Index.
“This is the first time I have a player like him, unfortunately only on loan from Liverpool.
“Before the Bundesliga game we had an exhibition match between Hertha 'A' and 'B' teams. Grujic was on the 'B' team, and they won 1-0.
“But it doesn't matter what I think of him, the numbers talk for themselves.
“When he started and played a lot we had a 2.4 point average. He has the whole team on his shoulders.
“With this point average we would contend in the Champions League. Top three teams in the Bundesliga have a point average like this.
“If he doesn't do anything, he still makes all the others calm with his presence. You know, he provides stability.
“Without him, we have a 0.7 point average. We would be relegated with this kind of performance.
“When he did not play, it affected all the others. We missed him in the middle of the park. We can have a good spring if he's healthy."