Liverpool boss Arne Slot described Paris Saint Germain's visit as the second of "three finals" in a week, but has warned much more is needed from the Premier League leaders to progress to the Champions League quarter-finals.
The Reds escaped the Parc des Princes with a 1-0 lead last week despite being battered by the French champions, who came up against an inspired Alisson Becker in the Liverpool goal.
The Brazilian number one said his nine-save display was the "performance of his life".
Never before have Liverpool won the first leg of a European tie away and let the lead slip at Anfield.
However, Slot is taking nothing for granted based on what he saw from PSG.
Luis Enrique remained upbeat his side are "going to do it" despite suffering a first defeat in 23 games.
Adding to Slot's concern was the lethargic first 45 minutes from his side against rock bottom Southampton in Saturday's 3-1 win that forced the Dutchman into three half-time substitutions.
The Saints, who have won just nine points from 28 games all season, took a shock lead into the break before Darwin Nunez and two Mohamed Salah penalties turned the game around to stretch Liverpool's lead at the top of the Premier League to 15 points.
The League Cup final against Newcastle is also around the corner on Sunday with Slot very much on track for a treble in his first season in charge.
"The first of three finals," he said of the victory over Southampton. "I do hope the next two finals we will play a bit better than the first one.
"The only good thing in the first 45 minutes was that they saved their energy (or PSG) and didn't run at all. It was maybe the first time this season I saw this tempo.
"When I look at the game against PSG, we need to go one step up in terms of intensity. But if I compare it with the game today (Saturday), we need to go three, four, five, six or seven steps up in terms of intensity if we want to have any chance of reaching the next round."
Salah conceded that he had rarely seeing his manager so furious as he was during a half-time tirade that helped the turn the Southampton game around.
"The manager was like going for us," said the Egyptian. "That's something you need sometimes."
Slot has had little reason to lose his cool in his first nine months as Jurgen Klopp's successor.
But he has shown his ruthless side when needed to keep Liverpool on course for just the fourth treble for an English side that would include the league title and Champions League.
Meanwhile, Bayer Leverkusen coach Xabi Alonso must channel the "Miracle of Istanbul", Liverpool's incredible comeback to win the 2005 Champions League final in which he was key, to overcome Bayern Munich on Tuesday.
On that day, then Liverpool midfielder Alonso scored the equaliser against AC Milan as the Reds came from 3-0 down at half-time to draw 3-3, before winning the match on penalties.
After Bayern's 3-0 win in Munich in the first leg of their last 16 tie, the deficit is the same for Leverkusen and Alonso going into the return fixture.
Leverkusen, the defending German champions who had never lost to Bayern in six matches under Alonso, capitulated in Munich last week, with the Basque lamenting a "self-inflicted" defeat where his side "gave everything" to their opponents.
Leverkusen's woes may be compounded by an injury to midfield lynchpin Florian Wirtz, who limped off after a rough challenge on Saturday having played just 14 minutes.
With this season's final in Munich, Bayern were under more pressure than Leverkusen heading into the first leg.
But after a goalkeeping howler, an unnecessary penalty and some poor marking for a Harry Kane header, Bayern have one foot in the quarter-finals.
Leverkusen have not made it as far as the last eight of the Champions League since their run to the final in 2002, where they lost to a Zinedine Zidane-inspired Real Madrid.
A two-time Champions League winner as a player, Alonso has outlined the scale of the task now awaiting his side, but knows from experience anything is possible.
"After this game we'll need a bit more time so we can recover -- in football we've seen big miracles quite often and we almost need one," he said on Wednesday.
"It's football, it's not my first time (against the odds), and there's another game at home."
Alonso may be relatively inexperienced -- this season is his first coaching in the Champions League and his second full campaign at the top level -- but he has already performed even greater miracles in the Leverkusen dugout.
Weighed down by the unwanted 'Neverkusen' moniker having never won the Bundesliga in their 120-year history, Alonso took over with the club in relegation danger in October 2022.
Alonso had an almost immediate impact, reviving the club's fortunes as they stacked up a series of victories including a 2-1 defeat of Bayern, Julian Nagelsmann's last match in charge of the German giants before getting sacked.
The following season, Alonso piloted Leverkusen to an unprecedented unbeaten league and cup double, along with a run to the Europa League final.
That Europa League final defeat was Leverkusen's only loss in 53 games last season.
Alonso's men scored 17 stoppage-time goals in all competitions, showcasing a self-belief which stayed resolute until the final whistle.
Agence France-Presse