And it was the usual suspect Lionel Messi that opened the scoring in the 27th minutes as he showcase his brilliant free kick ability, from a long distance.
And El Zhar made up for that miss 22 minutes from time, picking his spot in finding the bottom corner from 18 yards, with the aid of a slight deflection off Sergi Roberto, after being set up by Gabriel Pires. Left back Jordi Alba has undergone the most dramatic transformation under Valverde after falling out of favour under Luis Enrique, and has developed a particularly profitable understanding with Messi. And this was yet another display of the Argentinean's brilliance, with Barcelona once again dependent on their number 10.
After being picked out by Philippe Coutinho, Messi then doubled the score-line, holding off two defenders before finding the net with a trademark finish, which he nearly passed into the goal.
"It's what I've always done and if I can do it with goals, even better". The FC panel break down how big of a concern are Barcelona's underwhelming performances in the Champions League. They are seven games short of becoming the first team to complete a 38-game Liga season unbeaten.
Marcelino's team have had a fine campaign and even challenged for the title earlier this season, before suffering a drop in form.
By the victory, the Catalan side have matched Real Sociedad's unbeaten run between 1979 and 1980.
Barcelona's defence has been their great strength, but there's no doubting the team switched off after going two goals up.
Ernesto Valverde's men now turn their attention to Tuesday's Champions League quarter-final tie against Roma - where they hold a 4-1 lead - as their pursuit of a treble continues, while 14th-placed Leganes are left to reflect on a 12th consecutive league away game without a victory.
It's suggested Villarreal and Celta Vigo are also keen.