Chelsea's last clash against Liverpool came back in November 2012 - at a time when Roberto Di Matteo still managed the club, when John Terry was a first choice in the back four, and Brendan Rodgers had restored to a 3-5-2 formation and playing Jose Enrique in the attack.
A lot has changed between then and now. Rafa Benitez is now Chelsea manager, and although, like Di Matteo, he has settled on the Oscar-Mata-Hazard trio supporting Demba Ba as his first choice side, he now emphasises more caution in games. Brendan Rodgers, on the other hand, has overseen a rapid change of personnel, particularly in the attacking department.
Stewart Downing has enjoyed a return to the form he showed at Aston Villa, and he can play on either flank, but it is more likely that Jordan Henderson will start, either in the centre of the park to provide more energy, or in a narrow role on the wing, drifting inside quickly to become an extra man in the centre. It was the latter role he played against Reading, freeing up Luis Suarez to ‘in the hole' behind former Chelsea striker Daniel Sturridge. In his short, injury-affected time at the club, centre forward has been Sturridge's most common position, using his pace to play off the shoulder of the defence and make threatening runs in behind.
"Daniel's best position is as a central striker," says Rodgers. "I have said that 4-3-3 will become richer because of the type of players. There is not one way to play 4-3-3. You can have one up and two wingers, a floating nine like Luis Suárez, you can have one like Daniel Sturridge central, two in and around him narrow with full backs bombing on. The principles of your game are based on your players."
That underlines a common theme of Rodger's tenure so far, an emphasis on versatile attackers able to play in multiple positions. Phillipe Coutinho fits into this mould, able to play anywhere across the attacking band, and he will surely play some role here, cutting inside from the flank to become an extra playmaker. Chelsea must be wary of his threat in between the lines, but as Coutinho's timid performances against West Ham and Stoke suggest, keeping it tight between midfield and defence and not marking him tightly, which otherwise allows him to turn quickly on the ball and dart into the space behind, will nullify his presence.
The same goes for Luis Suarez, who for all his off-field tribulations is a brilliant player on it. In an interview with the Guardian, he appeared remarkably intellectual. "If I am playing centre forward hereand I drop off the front into this area, both centre backs might come with me in England," he said. "And then a team-mate can go into the space and be one on one with the goalkeeper."
That's Suarez describing the relationship between himself and Sturridge - and having seen Aguero and Tevez play successfully in this manner against Chelsea in the FA Cup semi-final, Rodgers will be encouraged to be bold with his selection, and try and work the spaces in behind Chelsea's back four.
That means he'll only have room for a midfield two, and that will almost certainly be the pairing of Steven Gerrard and Lucas Leiva that he has preferred for Liverpool's last three matches. There is the obvious division of roles, with Gerrard making more forward runs than his Brazilian counterpart. Lucas's return to the side has had a positive impact on Liverpool's defensive solidity - he reads the game superbly and completes the most tackles per game of anyone in the league.
"You see with Lucas, all of a sudden, you put the right profile of player in the right position, and it frees up your offensive threats," said Rodgers back in October. "He gives us great stability when we haven't got the ball, he intercepts, his transition is good and he gets the ball back quickly."
The security of Lucas also allows Gerrard to try more ambitious passes, and although the Englishman's passing range can be wildly inconsistent, he's capable of quick, direct balls to launch counter-attacks, and it was his clever pass towards Coutinho that triggered the move that lead to Liverpool's first goal against Aston Villa.
Chelsea must also be wary of the energy from midfield - part of Rodgers' philosophy is to have his side play high up the pitch, which comes in hand with intense pressing all across the field. Suarez with his boundless energy will set the tone, but it is in the midfield zone, where Gerrard and Lucas will push high up against Ramires and John Obi Mikel, where Chelsea must be careful. Rodgers is all about possession but his side are perhaps more devastating with their rapid transitions.