The Reds missed a golden chance to take one giant leap towards a Wembley final in the Carabao Cup semi-final first leg at Anfield on Thursday.
Mikel Arteta's side played most of the game with 10 men after Granit Xhaka was sent off in the 24th minute.
But without Mo Salah and Sadio Mane, who are away at the African Cup of Nations, Liverpool struggled to break resolute Arsenal down.
Here are three players walking the selection tightrope.
The right-back has been one of Liverpool's top performers this season.
With two goals and 12 assists already under his belt, it's fair to say Alexander-Arnold has bounced back superbly after a difficult 2020-21.
However, the England international delivered what many people will agree was his worst performance of the campaign.
His set-piece deliveries were inconsistent, with one corner not even getting past the first man.
He also struck a free-kick into the wall from a dangerous position, while several passes went astray. In fact, his pass completion of 79% was the worst of the starting XI.
The display was uncharacteristically Trent Alexander-Arnold. The opposite of what’s expected.
Klopp admitted that the defender's recent recovery from Covid-19 was a reason for his substitution in the 75th minute.
Neco Williams, who replaced Alexander-Arnold, was eye-catching during his cameo. The Welshman was lively and increased Liverpool's attacking threat.
With that in mind, Klopp could be tempted to give Alexander-Arnold a rest and allow him to be revitalised for the second leg against Arsenal.
Liverpool are already three centre-midfielders short.
Injuries to Thiago Alcantara and Harvey Elliott, along with the absence of Naby Keita due to AFCON, means Klopp's options have been decreased.
Fabinho and Jordan Henderson are the two regulars in the middle of the park.
It was James Milner who was given the nod over Alex Oxlade-Chamberlain and Curtis Jones to feature against Arsenal.
Perhaps this was somewhat of a surprise and it quite simply didn't work out.
There wasn't enough creativity in the engine room. There was lack of thrust and dearth of spark.
All of the good work from the middle of the park came from Joel Matip's marauds.
To be frank, Liverpool cannot start a similar three-man midfielder against Brentford. More is needed in terms of creating goalscoring chances.
Milner was the first to be withdrawn on the hour mark for Jones, who helped pep up the Reds.
That’s a change Klopp could make from the outset against Brentford.
The Japan international was the hero of the quarter-final win over Leicester when he bagged a stoppage-time equaliser to send the game to penalties.
However, he was very much the villain on this occasion.
Minamino was gifted a glorious opportunity in the 90th minute to win the game for Liverpool. When the ball dropped to him 10 yards, the empty goal was gaping.
However, he instead sent his effort well into the Kop.
It typified Minamino's two-year Anfield career. He's failed to build any sort of momentum or consistency.
The makeshift front three that also included Diogo Jota and Roberto Firmino were short of ideas throughout.
All three players are of a similar ilk. None have the burning pace or ingenious to break the line and get away from their marker.
Given Jota and Firmino have firmly been in Klopp's plans this season, Minamino is the likely candidate to be axed if a change is made.
The Liverpool boss could opt to play Jones or Oxlade-Chamberlain in an advanced role.
Teenager Kaide Gordon, who scored against Shrewsbury in the FA Cup win last weekend, is also an option.
The ideal scenario would be that Divock Origi returns to full fitness but that doesn't look like it will be the case. He only started running outside on Thursday.