Liverpools captain was left out of the travelling squad to play Toulouse but there are no long-term worries about his fitness.
Manager Klopp explained: Virgil is a little bit ill.
Should not be big thing, but didnt want it to happen on the plane, its obvious. Maybe some others have it as well, I have it.
He should be alright for the weekend.
There is a good chance Van Dijk would have been rested for this one anyway. With Jarell Quansah stepping up in cup competitions, there should be no worries about the strength of Liverpools defence.
Quansah and Joel Matip are expected to start together, while Joe Gomez and Ibrahima Konate are also available should they be needed.
Two players Liverpool wont be able to call upon, though, are Curtis Jones and Ryan Gravenberch.
After the pair missed training, the manager explained their absences. Klopp said: Curtis had last week a hamstring [problem], not massive.
After the international break, he will be back, but not before. Low, low grade hamstring.
On Gravenberchs issue, Klopp was more positive, saying: Ryan got a little niggle knee. He was running today (Wednesday) already, but there was no chance for this game.
There is a chance for Brentford and he will definitely be back after the international break.
With Stefan Bajcetic and Thiago also still out, Liverpool will likely start with a midfield of Wataru Endo, Harvey Elliott and Alexis Mac Allister.