Madrid - Lionel Messi and Luis Suarez might be the deadliest attack in Europe but Barcelona's success in the Champions League could rest on their increasingly mean defence.
After their 1-0 win over Manchester United at Old Trafford on Wednesday, Gerard Pique said Barca are tighter at the back than they have been all season.
"We put in an excellent performance defensively, we're in our best form in defence of the season," Pique said.
"The early goal relaxed us and we knew how to cope with the situation, the fact we didn't concede helps us a lot."
Barcelona face a trip to La Liga's bottom-club Huesca on Saturday, when Ernesto Valverde is likely to rotate his line-up ahead of the return leg against United three days later.
An 11-point lead at the top of the table has earned Barca that luxury, while United face West Ham the same afternoon, still scrapping for a place in the Premier League's top four.
To turn the tie around, Ole Gunnar Solskjaer's team will have to score at least once at Camp Nou, where their opponents have endured only one defeat in 52 matches and, in the Champions League, one in 10 years.
Nerves could yet affect Barcelona, whose entire season seems to hinge on their performance in Europe, but they now have a defence too that can step up when the attack stalls.
Messi, bruised and bloodied, was quiet against United, a muted display typical of his team, who struggled for their usual fluency going forward.
Instead, it was Pique that shone, the 32-year-old delivering arguably his best showing of the season as part of an impressive, disciplined defensive display.
"We were very conscientious," said Jordi Alba. "Sometimes you go on the attack and leave the defence open but we sat in more and balanced the game."
Under Valverde, Barcelona's free-flowing, passing style has been given a more pragmatic edge, with solidity and athleticism deemed key ingredients to allow Messi and Suarez to thrive.
But the defensive rigour had slipped. After conceding less than half a goal a game in the first half of Valverde's opening campaign, Barca were conceding more than a goal a game for the second half of last season and the first half of this one.
Four league matches without a win in September and October were underpinned by errors at the back.
There are signs though that they have tightened again. In the last 12 league games they have kept six clean sheets, with the goals conceded now back below a goal per game.
In all competitions, they have shut out Lyon, Real Madrid, twice, Atletico and Manchester United in the past three months alone.
"Pique and Lenglet are a great pairing, they are the security for us," Sergio Busquets said on Wednesday.
"They are playing at a very high level," added Valverde.
Barca's dominance means Real Madrid and Atletico are left battling for second place, with Real away to Leganes on Monday after Atletico host Celta Vigo on Saturday.
Diego Simeone will be without Diego Costa, who has been handed an eight-match ban by the Spanish football federation for insulting referee Gil Manzano during last weekend's defeat at Camp Nou.
Atletico have appealed but if unsuccessful, Costa will not play again this season.
Real are now only two points behind their city rivals ahead of their game against Leganes, with all eyes on Zinedine Zidane's team selection again.
Gareth Bale endured another difficult afternoon as Real scraped past Eibar last time out and it remains to be seen if the Welshman keeps his place.
Whistled again by supporters at the Santiago Bernabeu, Bale's future in Spain has perhaps never looked less certain.
"Bale, with all his experience, is used to it," said Casemiro on Thursday. "When the fans whistle a player, they are whistling all of us. We cannot forget the titles and goals that he has given us."
Fixtures (all SA time)
Espanyol v Alaves (14:00), Huesca v Barcelona (17:15), Atletico Madrid v Celta Vigo (19:30), Sevilla v Real Betis (21:45)
Real Valladolid v Getafe (13:00), Athletic Bilbao v Rayo Vallecano (15:00), Real Sociedad v Eibar (17:15), Girona v Villarreal (19:30), Valencia v Levante (21:45)
Leganes v Real Madrid (22:00)