Chelsea are in FA Cup action as they face runaway Premier League leaders Liverpool at Stamford Bridge in the fifth round of the competition.
The Blues go into the game off the back of a 2-2 draw with AFC Bournemouth in the Premier League on Saturday, while Jurgen Klopp's team will be looking to bounce back from their first league defeat of the season.
Liverpool's bid to match Arsenal's Invincibles was halted with a 3-0 defeat to Watford at Vicarage Road on Saturday evening in one of the shock results of the season.
Both teams will be desperate to make it through to the quarter-final of the competition, but with the unusual situation with the game being played in midweek, what happens if it ends in a draw after 90 minutes?
Here's everything you need to know about the match.
Is there extra time and penalties?
Chelsea could face extra time for the second match in a row if the score is level after 90 minutes, which would see another half an hour of football played at Stamford Bridge.
Replays are not played from the fifth-round onwards, which means that they do not have the option of a second match at the Anfield.
if the score is still level after 120 minutes, there could also be a penalty shoot-out.
Can a fourth sub be used?
If the match progresses into extra time, Chelsea will be allowed to make a fourth substitution in the additional 30 minutes that are played.
The rules state: "In the event that extra time is played in any match a Club may at its discretion use one additional substitute player, (a fourth in total) from the nominated seven substitutes, during such period of extra time."
