'Players only human,' says Klopp as Liverpool survive collapse to reach semi-finals

Klopp's side already had one foot in the last four after winning 3-1 in the quarter-final first leg in Lisbon.

They were on cruise control for long spells in the second leg at Anfield, but had to hold their nerve before advancing 6-4 on aggregate after an uncharacteristic meltdown in the closing stages.

Ibrahima Konate put Liverpool ahead before Goncalo Ramos equalised late in the first half.

When Roberto Firmino netted twice after the interval, the tie looked all but over.

However, Roman Yaremchuk and Darwin Nunez struck for Benfica to briefly give the visitors hope of an astonishing escape act, before Liverpool finally restored order.

"When I'm not over the moon about qualifying for the Champions League semi-final, something is really wrong and maybe I should quit!" Klopp said.

"The situation was the defence had never played together and it was about details, staying 100 percent concentrated.

"We were 6-2 up on aggregate. The players are human beings, they were like 'Ok job done'. But Benfica kept fighting and I respect that.

"It was not exactly what we wanted but it is absolutely not important. We are through and that's all that matters. I'm really happy."

The Reds will face Spanish side Villarreal in the semi-finals as they look to reach their 10th Champions League final and claim a seventh title in the competition.

Despite Villarreal's impressive wins over Bayern Munich and Juventus in the last two rounds, Liverpool will be firm favourites to make a third Champions League final in the last five seasons.

"To beat Juventus and Bayern Munich, they deserve to be in the Champions League semi-finals. Unai Emery is the king of the cups, it is unbelievable what he is doing. But give me a bit of time to prepare it properly," Klopp said.

Liverpool sit one point behind Premier League leaders Manchester City after Sunday's draw against their title rivals.

In the midst of a run that will define Liverpool's season, Klopp was able to keep Mohamed Salah, Sadio Mane and Virgil Van Dijk fresh as he started with his stars on the bench ahead of Saturday's FA Cup semi-final against Manchester City.

- Firmino stars -

Konate had headed the opener in the first leg at Benfica and Liverpool's towering centre-back tormented the Portuguese side with his aerial prowess again in the 21st minute.

Kostas Tsimikas whipped an outswinging corner towards Konate and he climbed above three Benfica players to head into the far corner from 10 yards.

Benfica snatched their equaliser against the run of play in the 32nd minute.

Diogo Goncalves' pass clipped off James Milner and ran through to the unmarked Ramos, who smacked a fine finish past Alisson from just inside the area.

Any hopes of a stunning Benfica fightback seemed over when the visitors shot themselves in the foot in farcical fashion in the 55th minute.

Goalkeeper Odysseas Vlachodimos was the instigator of Benfica's meltdown as he fumbled what should have been an easy interception of Naby Keita's over-hit pass.

Jan Vertonghen's panicked attempt to clear the danger wasn't much better and Jota crossed back into the six-yard box, where Firmino had the simple task of tapping into the empty net. 

Firmino followed his first home Champions League goal for two years with another 10 minutes later.

Tsimikas curled a superb free-kick to the pass and Firmino eluded Benfica's sloppy marking to volley home from close-range.

With Klopp's men taking their foot off the gas, Yaremchuk struck in the 73rd minute, rounding Alisson to slot home after beating Liverpool's offside trap.

There was a sharp intake of breath around Anfield when Nunez scored with a predatory finish in the 82nd minute.

Moments later, Nunez's low strike tested Alisson, but Liverpool held on to keep the quadruple dream alive.