Dier was absent for the wild 3-3 draw with West Ham on Sunday with a hamstring problem sustained on England duty and he is still not fit enough to return, leaving Jose Mourinho short of centre-backs.
Japhet Tanganga (thigh) is also sidelined and new signing Joe Rodon is ineligible for the Europa League.
In a boost to the Spurs manager, Giovani Lo Celso and Erik Lamela both trained after missing West Ham with knocks and should feature against the Austrian side.
Mourinho is set to rotate his squad after his side shipped three goals in the final eight minutes in an unprecedented collapse against the Hammers, with Gareth Bale is pushing for a first start after coming off the bench with Spurs 3-0 up.
Summer signing Carlos Vinicius is expected to make his debut, while Mourinho must also decide if Dele Alli will feature after again leaving the England international out of the squad entirely on Sunday.
Predicted Tottenham XI to face LASK (4-2-3-1): Lloris; Doherty, Alderweireld, Sanchez, Davies; Lo Celso, Winks, Ndombele; Lucas, Kane, Bale