Karius, brought in from Mainz for £4.7 million in the summer, will keep his place between the sticks after making his competitive debut for the club against Derby County in mid-week.
Though the German, who had spent two months sidelined with a broken hand, had little to do, he kept a clean sheet as the Reds won 3-0 to progress to the fourth round of the EFL Cup.
Liverpool boss Jürgen Klopp will now entrust the 23-year-old to maintain his starting spot over Mignolet, who had started all six of the Reds' games so far this season prior to the trip to Derby.
It was thought that the Belgian, who only signed a new five-year contract in January, might have done enough to keep his place as No.1 - but he was told at their Melwood training ground on Friday that he would be dropping to the bench for the visit of the Tigers.
Liverpool go looking for a third straight Premier League win, and a fourth successive victory in all competitions, against Mike Phelan's men at Anfield as they look to maintain their fine recent form.
Karius to be picked over Mignolet for Hull tie
Karius will hope to make the kind of impression that boosts his chances of remaining the manager's first-choice for the forseeable future, with the Germany Under-21 international expected to be Klopp's long-term No.1 shot-stopper.
Formerly of Manchester City's Academy before moving to the Bundesliga, Karius played just short of 100 times in the German first division and it is no secret that his compatriot Klopp rates him highly.
He was initially signed as competition for Mignolet, albeit with the view to displacing him over time.
Mignolet, who joined back from Sunderland in 2013, has had a frustratingly inconsistent few seasons with the club, but has performed solidly thus far this season, though he hasn't kept a clean sheet in the league.
However, Klopp's decision to drop him in favour of the fit-again Karius suggests that it is the Reds' summer addition who will be his immediate first-choice this term - despite recent comments in his pre-Hull press conference stating otherwise.
The Reds boss told reporters that whoever he selects against doesn't mean they will remain in goal "for the next five years" and declared himself "really happy" with both goalkeepers, insisting his decision will be the best suited player for the team against Hull, rather than a comparison between the two.
But the uber-confident Karius will be afforded the opportunity to prove he should be picked ahead of Mignolet, who - for the first time in his Liverpool career - could face a sustained spell on the bench as back-up.
Elsewhere, Dejan Lovren is expected to return to the side with Joel Matip in central defence ahead of Karius, with a similar side to the one that won 2-1 at Chelsea last Friday - potentially plus midfielder Emre Can - expected.