Barcelona is a rock. Barcelona is an island.

Around it, the seas roil. Real Madrid claimed three Champions League titles in four years and looked poised to take the title of the world’s top team from Barca, only to slip into a slump to start this La Liga season. Atletico Madrid is fading from its years-long challenge to the Spanish duopoly. And in the group stage of the Champions League, not even Juventus could really put up a fight against the Catalans.

Domestically, the only team within single-digit points of leaders Barca going into Sunday was Valencia, trailing by four. Valencia is a new rival. Or an old new one. After two straight seasons of 12th-place finishes, each of them seeing four managers try and fail to get the southern Spanish giants back on track, Marcelino has finally gotten it right.

On Sunday, Valencia very nearly handed Barca its first defeat of the season proper. The Catalans had yet to lose a competitive game this season, unless you count the inexplicable 5-1 aggregate, two-leg plastering at the hands of Real in the Supercopa de Espana, which isn’t really considered part of the season. The Champions League group stage was a stroll. And an 11-0-1 start to the league season put significant distance between Barca and all the rest at an early stage.

Only Valencia had managed to hang tight.

And on the strength of an unforgivable mistake by referees and a night on which Barca largely dominated yet struggled to create chances, Los Che very nearly snagged a victory, settling for a 1-1 tie instead.

During the first half, Barca was in total control, efficiently pinging the ball around and pinning their hosts back. Yet real opportunities were scarce. Barca should have gone ahead after half an hour. But a blunder by goalkeeper Neto was canceled out by a blunder from one of the assistant referees.

Neto fumbled a routine Lionel Messi shot, ripped right at the goalie’s hands. The ball skipped through his legs and bounced well behind the line, before caroming back out. It was not given. And since there is no goal-line technology or video-assistant referee in the Spanish league, there was no technological recourse to such a grievous oversight.

Worse still, Valencia very nearly capitalized as Barca was distracted, protesting the controversial decision. The Bats scampered up the other end of the field, where Simone Zaza zipped a shot just wide — the first of several times the Italian striker would waste hopeful chances.

After the break, Valencia was the better side for a good half-hour. Barca goalie Marc-Andre Ter Stegen kept the opposition at bay when he denied the rampant winger Goncalo Guedes — the 20-year-old Portuguese sensation on loan from Paris Saint-Germain — one-on-one.

But a few minutes later, Valencia executed a perfect overlap up the left flank. Rodrigo got away from defender Thomas Vermaelen and redirected the low, hard cross from Jose Luis Gaya into the net.

Valencia then had several shouts for a penalty kick, which were all denied. The one from Guedes, claimed against the otherwise unimpeachable Samuel Umtiti, had the most merit and should probably have been given.

But as Valencia got greedy and pushed for a second goal, Barca found a well-earned equalizer. Messi, who had been rested against Juventus in the Champions League on Wednesday but had mostly been pedestrian by his standards, picked out Jordi Alba streaking toward the far post.

And Alba, playing against his old club, which has never quite forgiven his departure, it seems, finished with a marvelous diving volley to make it 1-1. It was his first goal of the season.

On a difficult night, Barca churned on and got the result, preserving its unbeaten status.

Because Barca is a rock. And an island.

The fortunes of others rise and fall and rise again. But Barca stays the same, at the top, immovable. Even its region, Catalonia, lives through turmoil as an unsanctioned referendum recently sought to declare independence from the rest of Spain — raising the question whether the club would still be welcome in the Spanish league — which was summarily struck down by the government in Madrid.

Again and again, Barca’s decade-long dynasty has been eulogized, only for the club to carry on winning as if nothing ever changed. When Xavi aged out and moved on to a final payday in Qatar, that was supposed to be the beginning of the end. Since then, several other factors were seen to signal demise as well: the frequent managerial turnover; the aging of Andres Iniesta; the core of Messi, Gerard Pique, Sergio Busquets and Luis Suarez all hitting age 30; Neymar’s departure last summer.

Yet Barca is the favorite for a jaw-dropping seventh La Liga title in a decade. It still leads Valencia by four points — and Atletico and Real, who picked up two points in the race, by eight. After 13 rounds, Ernesto Valverde’s side has the most goals scored — 34 — and the fewest conceded — 5.

Not bad for a team that’s supposedly on its last legs, for a dynasty that’s been dying for years.

Leander Schaerlaeckens is a Yahoo Sports soccer columnist and a sports communication lecturer at Marist College. Follow him on Twitter @LeanderAlphabet.