On a bitterly cold night at Anfield, Liverpool were well below their best and Porto deserve credit for a determined performance after going two goals down in 26 minutes. This was Fabinho-Keita-Henderson, the midfield that - to borrow a Jose Mourinho expression from his Real Madrid days - represented Klopp's high-pressure triangle.
Firmino doubled his side's lead, tapping home from close range after Trent Alexander-Arnold sent a low cross into the six-yard box.
Alisson's left foot denied him at first after he was slid in behind the Reds' defence, before he shot straight at the Brazilian as Liverpool failed to clear a corner and left the striker unmarked in the box.
Manchester United, should they prevail over Barcelona, will face the victor of Liverpool vs Porto in the semi-final on the other side of the draw. It is Liverpool's evolution under Klopp that is the greatest victory of all.
Three US soldiers killed in Afghanistan
The Taliban have held talks with a USA envoy in recent months while continuing to carry out daily attacks on Afghan forces. Abdullah said the Taliban could partake in elections and even compete for the presidency if they renounce violence.
He now has two goals in as many games, and could have a key role to play in the most important part of Liverpool's season.
Porto are also involved in a top-of-the-table tussle which looks set to go down to the wire, with only goal difference separating them from leaders Benfica ahead of Saturday's visit to Portimonense.
"We hoped it would be like this because the last game he got better and better until the last minute so we wanted to build on that", said Klopp. It's a lovely, lovely team goal.
"We also saw one or two counter attacks, but the rest of the game we played really well". "They must feel - the players, Jurgen, the fans - that they'll go there and score". In stoppage time, with Liverpool looking tired after their efforts throughout the game, it was Keita still charging forward, bursting past a couple of opponents into the box.
"Hendo's a brilliant player and I'm really happy he can show that again", grinned Klopp in his post-match news conference.
Keita put in arguably his best performance in a red shirt since joining in the summer and after a hard settling-in period appears to be fulfilling the faith Jurgen Klopp placed in him in agreeing a deal with RB Leipzig 12 months before he actually arrived. He obviously likes the position. Liverpool enters the tie as the heavy favorite to move on, but Porto knows all about being a dark horse in this competition.