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.
Celta Vigo gave their hopes of playing in Europe a big boost as Lago Aspas scored a hat-trick in their 4-0 win at home to Sevilla, who looked exhausted following their Champions League game on Tuesday and who are suddenly in real danger of not qualifying for Europe next season. Five minutes later the Argentine doubled the lead, taking one touch to control a through ball from Philippe Coutinho before delivering a cool low finish.
But Leganes could not make the most of their goal, and with three minutes to go Ousmane Dembele found Messi who chested the ball down then clipped it over the advancing Cuellar, with mercurial style.
For extra motivation, the Blaugrana can reach 38 games without loss if they avoid defeat here - a run that would match Real Sociedad's national record from 1979/80.
Police say 6 detained in foiled plot to attack Berlin half-marathon
The German daily Die Welt first reported that police foiled a plot to attack race spectators and participants with knives. Authorities said the attacker had stored several gas bottles and canisters with gasoline and bio-ethanol at his home.
"We are still winning and we are growing in every game".
Barca to win to nil is priced at 8/15 (1.53), although more appealing is the price of 9/10 (1.90) for Valverde's side to win with a -2 handicap. "We have to keep fighting until the end, just like our other rivals".
First, having been hacked down by Dimitrios Siovas 25 yards from goal, Messi got up and took the resulting 27th-minute free-kick himself, finding the corner from with a magnificent whipped effort that left Cuellar with no chance.
Betis temporarily at least, moved into fifth place with a 2-0 home victory over Eibar thanks to Sergio Leon's 11th goal of the season and an own goal from Anaitz Arbilla.