Diaz was sold by the Reds to Bayern Munich in August.
Defeat at Chelsea last night was a third on the bounce for Liverpool and Sturridge said on Sky Sports: "Luis Diaz is a massive miss for me. When you look at Liverpool last year and how they used to press, I think arguably he was the one who would set the press in the front three. (Dominik) Szoboszlai would do it in the midfield with that power and dynamism that he has.
"For me, Luis Diaz, how tenacious he is on the ball and how hungry he is to get it back for his team. He brought something to Liverpool that they are now missing. I think (Hugo) Ekitike and (Alexander) Isak and (Florian) Wirtz work hard, I'm not saying they don't. We can't question their work rate or their quality.
"But what I will say is that they're attack-minded players. I think with Diaz would sacrifice himself defensively. That's what they've got to figure out now, who in that attack is going to give themselves up a little bit. In a front three there always has to be one guy who goes, 'I'm not stats hungry'.
"You see (Cody) Gakpo this year scoring more goals, (Mohamed) Salah scoring less, the new strikers want to hit the ground running. So I think, Jamie (Redknapp) questioned the balance in the midfield, but I also think it's in the front three.
"It's important to understand which one of three is going to be the workhorse, who's going to be the one who does what he wants and who's going to be a hybrid of both. Right now, I'm not sure the manager knows what he's going to do."