LONDON — Possession in soccer is not even one-tenth of the law, and goals are the only statistics that count in winning or losing matches.

Right now, Barcelona is the best team in the world, and it has the titles to show for its marvelously appealing style of play. But in the span of just four days starting this Saturday, Barça could lose both the Spanish league and the Champions League trophies it now holds.

Lionel Messi and company are down in both competitions. They lag four points behind Real Madrid in La Liga, and they trail Chelsea by a goal after losing the first leg of its Champions League semifinal, 1-0, in London on Wednesday night.

If there is to be salvation, it will come at the Camp Nou, where Barcelona hosts Madrid on Saturday and Chelsea on Tuesday.