The 26-year-old defender became the youngest player to reach a century of international appearances, and his 49th minute header seemed to be enough for Vicente del Bosque's men, who dominated throughout but were frustrated for long spells by the visitor's defensive approach.
But la Roja's inability to turn possession into goals cost them late on, as Teemu Pukki stunned the crowd by drilling home a 79th minute leveler to salvage a point for the visiting side.
Spain now falls two points behind Group I leader France, which the team visits on Tuesday, while Finland, despite the result, still remains bottom in the standings with only two points to its name.
Cesc Fabregas reprized his false-nine role as one of seven Barcelona players in the home side’s XI, which was a record number of starters from a single team in la Roja’s World Cup qualifying history.
Spain was quickly on the front foot, and nearly took an early lead when Nicklas Moisander inadvertently deflected Cesc Fabregas’ cross towards goal, forcing a fine reflex save out of Niki Manepaa.
The match soon settled into a familiar pattern, as Finland was penned deep in its own half by Spain’s tiki-taka football, with Pukki cutting an isolated figure alone up front for the visitors.
Manepaa smothered a close range effort from Andres Iniesta, but was forced to work a bit harder to beat away Santi Cazorla’s strike, after the Arsenal man had cut in from the flanks.
Cazorla then completely mishit a loose ball that caught the defense by surprise, before Finland belatedly sniffed out its first decent sight on goal when Roman Eremenko blasted about a foot over from outside the box.
The entirety of the match was being played in the offensive third, but not for the first time, Spain was frustrated by the sheer numbers at the back from its opponent, and could not muster much more than half-chances as the first half petered out.
With the conventional approach stymied, it took a more direct route for la Roja to break the deadlock, and it was Ramos who came up with the goods, heading in Silva’s corner minutes into the second half.
The goal seemed to unburden Spain, and Ramos, who was finding himself increasingly forward, nearly struck again when a rasping drive from him flew the wrong side of the post.
The home side was then up in arms when the referee waved play on after Fabregas was sent tumbling by Alexander Ring in the area, moments before Pukki shot wide on a rare Finland sighting in the opposition half.
But Spain was unable to seriously threaten again as the match entered its closing stages, and the team was pegged back with 11 minutes remaining when Pukki stole in between Ramos and Pique to turn home from close range.
Still, Spain had chances to win it late on, but Alvaro Negredo twice failed to convert, sending a header wide before he was denied by Manepaa. Finland became only the second team in seven years to avoid defeat away to the world and European champion.
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