In a fixture this tense, the live score will change the whole night.
If Rangers score first, the atmosphere at Ibrox becomes a serious factor. If Celtic go ahead, their control and recent consistency could make the tie feel long for the home side.
The key pre-match watch is how aggressive both managers decide to be with selection.
In a game like this, full-back balance, midfield legs and the identity of the central striker matter as much as any headline name. One conservative selection can make the contest cagey; one brave call can swing it.
On recent league form, Celtic appear to hold the narrower advantage. Six wins from six gives them the stronger platform, and that kind of run usually brings authority in big matches. But Rangers have their own streak, home advantage and the emotional pull of a cup tie under lights.
Expectation points to a one-goal game, extra tension and very little margin for error. The next big storyline will be the confirmed lineups, then whether the early scoreline forces either manager to abandon the original plan.