That doesn't happen very often, but everything changed in the second half. More specifically, in the 59th minute, when Luis Suarez's pass sent Ivan Rakitic scuttling through and the Croatia international broke the deadlock with a cute finish. Barca then proceeded to run riot, with Suarez and Lionel Messi scoring two goals each in a dazzling final 30 minutes that drew applause even from the Betis supporters. A number of the Betis players, too, admitted after the game that there's no stopping Messi when he clicks like that.

By full time, the five-goal win might have been deemed slightly harsh on Betis, but it also felt like just reward for the performances produced by Messi, Suarez and Rakitic.

It perhaps wasn't completely surprising, either. It took Barca's tally of league goals this season to 57, but, more interestingly, it took their tally of league goals in the second half of matches to 40. To put that into context, that's more than every other side have scored in La Liga in total with the exception of Valencia, who have netted 41. Real Madrid (who have a game in hand) have scored 39 in their 19 games, which includes the seven in Sunday's win against Deportivo La Coruna.

Maybe if Betis had scored during their best spells in Sunday's game, things could have been different. But then, even if they had, the numbers suggest Barca would have come on strong in the second half regardless.

Betis join Alaves, Las Palmas, Villarreal and Madrid on the list of teams that have fallen to Barca in the league this season after reaching halftime level at 0-0. Ernesto Valverde's side have also come back from 2-1 down at the break to beat Real Sociedad 4-2, from 1-0 down to beat Getafe 2-1 and from 1-0 down to draw with second-place Atletico Madrid. They also scored a late equaliser at Valencia, although both goals in that 1-1 draw came in the second half at the Mestalla.

"Valverde reads the games well and gets everything right," Alba said after the Betis game, piling the credit for his side's second-half performances at his coach's feet. "At halftime, when he has more time to speak with us, he changes things, and he's really good at it. That's important."

Teammate Suarez, who moved on to 15 league goals with his brace in Seville on Sunday, says it's about fitness.

"We are aware that teams play with a lot of intensity against us early on," said the Uruguay striker. "But we're still good physically in the second half, we're strong and we're showing that we had a good preseason and are in good shape."

Valverde says fitness obviously has something to do it but also says the idea is not to soak up the pressure in the first half before attacking after the break.

"The fact we're resolving so many games in the second half has something to do with fitness, but it's always our intention to go out and win the game from the first whistle," said the coach during a news conference last week.

"It's true that performances in the second half of games have been at a particularly high level. Maybe it's down to the style because it's tough for the opposition to keep closing down space for such a long time. It's natural they may tire if [they're] pressing high, especially in the second half. But we don't go out with that as a plan. We always go out to win from the first minute."

Patience is also a key. It's not necessarily a traditional Barcelona trait, but Valverde's side are capable of soaking up pressure if they have to, of waiting for the right moment to attack and of making sure they take their chances when they do arrive, be that in the first minute or the last.

"We knew it was going to be a tough game from the start and that [Betis] were going to try and press high and rob the ball from us," Rakitic said. "But we were patient and we waited for our moment to get that first goal and to find more space."

The patience paid off and the moment arrived, as did the space. And not for the first time this season. Unbeaten Barca have accrued 54 points from their 20 league games -- 11 more than second-place Atletico -- with 17 a direct result of second-half goals.

Is that down to Valverde, fitness, patience or belief? Probably a little bit of all of them.