Liverpool manager Jurgen Klopp. Picture: PAUL ELLIS/AFP via Getty Images
Liverpool renew their rivalry with Manchester City when they travel to Anfield on Sunday (16.30 BST).
Jurgen Klopp will have to get his team selection spot on in the battle between two Premier League title rivals.
The Reds boss has three dilemmas he needs to get right.
Does Firmino come back into the team?
Diogo Jota has crashed the party of Liverpool's renowned front three.
The Portuguese has plundered four goals in 11 matches so far this season, with his intelligent move also playing a key role.
However, Roberto Firmino - who's been at the fulcrum on the Reds' success in recent season alongside Mo Salah and Sadio Mane - has come back from a hamstring injury firing on all cylinders.
The Brazilian notched a double when introduced off the bench against Porto and will be desperate to win back his starting berth.
Klopp has to weigh up whether that audition was good enough to earn Firmino a place in his side.
The natural replacement would be for Jota, but Mane's also at risk.
The winger might have scored at Porto but his performances have been spluttering this season. In the 3-3 draw at Brentford, he was well below his best.
Klopp could be tempted to give Mane a breather and switch Jota to the left flank.
Will Jones keep his spot?
Curtis Jones' performance against Porto was rightfully lauded. He ran the show in centre-midfield.
Having been down the pecking order at the beginning of the campaign, injuries to Harvey Elliott, Thiago and, to an extent, Trent Alexander-Arnold have thrust him into the mix.
But City are in another stratosphere to Porto and it'll be a significantly tougher test for the 20-year-old against Kevin De Bryne and Co.
Does Klopp feel Jones has the maturity to feature in the engine room? And having started the past three games, will the academy graduate be suffering from fatigue?
Perhaps Klopp will factor in last campaign's 4-1 drubbing. Jones indeed started and, despite the scoreline, was Liverpool's most impressive player.
However, Naby Keita has now returned from a minor foot injury.
He would offer more nous and solidity in the middle of the park, although it would somewhat negate the Reds going forward.
It seems between those two to start next to Jordan Henderson and Fabinho, with Alex Oxlade-Chamberlain out of favour.
Who’s the man to thwart Grealish?
Klopp didn't give too much away about who will fill in for Alexander-Arnold.
On the past two occasions, the versatile James Milner has deputised and performed magnificently in wins over Crystal Palace and Porto.
The vice-skipper is again the leading candidate to start on the right-hand side of defence. It would be a surprise if Milner doesn't feature there.
However, Klopp could be tempted to have an out-and-out defender given they'll be marking City's £100 million summer signing Jack Grealish.
Joe Gomez has played right-back for the Reds on several occasions, albeit he's far better in the centre.
Klopp also mentioned 20-year-old Neco Williams is an option, although he's not too long back from injury.