This proved a torturous evening for Rafael Benítez, his side's inability to capitalise on territorial advantage against substandard opposition leaving him numbed as this arena erupted. That failing has cost Liverpool their Premiership challenge, now it undermines them in Europe. Benfica are deeply unimpressive yet, while the Champions League winners continue to ally sloppiness in their final pass with profligacy in and around the six-yard box, the Portuguese could conceivably squeeze through the second leg in a fortnight.
Benítez will be restless until that opportunity for redemption. The Spaniard scowled his way back to Lisbon airport in the aftermath last night, struggling to digest his side's first defeat in this competition since November 2004. Their superiority was evident from the opening exchanges but, damningly, their monopoly of possession failed to prompt a single shot on target. Then, 84 minutes in, the substitutes Dietmar Hamann and Giorgios Karagounis collided, the German was penalised and, from Petit's free-kick, Luisao darted around the back of Liverpool's dawdling defenders to flick a header beyond José Reina.
Too often recently, most notably at Old Trafford and Stamford Bridge, set pieces have floored Liverpool, for all that Benítez insisted his side concede "less than anyone else from set plays in the Premier League". Confusion still occasionally flares at his preferred zonal marking. "We've seen the trick they played on the videos but we did not react," said the manager. "No one picked up their man and that is disappointing."
Reina had not been beaten in European competition for 573 minutes, a club record set last night, but that was scant consolation. The nearest Benfica had come to piercing his resistance previously had been Petit's optimistic punt from the halfway line. In the frantic aftermath to the goal, Reina might actually have shipped a second only for Simao Sabrosa's lob to lack the height to trouble him.
As it is, Benítez will recognise that the Portuguese are vulnerable, even if much will depend upon whether the European champions can muster the tempo and bite to wound them. With Steven Gerrard only summoned from the bench 12 minutes from time here - the captain suffered a dead leg against Manchester United on Saturday - the Merseysiders lacked the thrust to convert their immaculate possession. Luis García's frequent overelaboration alone cost them the ball.
The former Barcelona midfielder was booked 29 seconds into this contest for a foul on Léo and missed the visitors' best opportunity, shanking a half-volley from Harry Kewell's centre wide in the opening exchanges of the second period. Fernando Morientes's rise and flicked header to John Arne Riise's throw-in might have earned the lead, but the Spanish striker misses more than he hits these days. Robbie Fowler, who was playing his first game in this competition since November 2001, watched those opportunities spurned with anguish, given that nothing as tantalisingly presentable fell to him.
What was all the more depressing for Liverpool was that they returned home last night without Mohamed Sissoko, the midfielder having been kicked in the head by Beto - who was booked for the challenge - to depart for the local hospital with "a serious eye injury" where he remains under observation.