The veteran midfielder came off the bench to score a stunning goal in the dying minutes, before the Blaugrana put an added gloss on the scoreline thanks to a Borja Gomez own goal
The midfielder came off the bench with the Blaugrana toiling and immediately added an attacking dimension, scoring with four minutes to play before Borja Gomez sealed his side's fate by diverting Lionel Messi's cross-cum-shot past his own keeper.
Despite starting as overwhelming favourites to record their fifth straight Liga victory, Barcelona began in muted fashion and could not find a way past a determined Granada team. The visitors defended with purpose and tenacity, and also threatened going forward with some swift counter play; Floro Flores standing out alone up front with some intelligent play.
Messi went close in the opening minutes, denied by the boot of Inigo Lopez after a sumptuous long pass from Dani Alves. But it was Granada who threatened early on. Flores took advantage of a misunderstanding between virgin defensive pairing Javier Mascherano and Alexandre Song to test Victor Valdes, before Mikel Rico fired just over when more uncertainty at the back saw a loose corner fall at the midfielder's feet.
Barca enjoyed a lion's share of possession, but too many missed passes saw the hosts attack without their customary precision and verve all too often. As the first half progressed, however, Tito Vilanova's men started to take a firmer hold on proceedings.
Cesc Fabregas forced a good save out of Tono after Messi's mazy run was cut short just inside the area. The Granada defence would give no quarter, though, and were led exceptionally by Lopez, who followed up his early block on Messi with several other decisive interventions to frustrate the favourites.
Borja Gomez perhaps went closest to opening the scoring for the home team: his misjudged header from Alexis' cross sent Tono scurrying back towards his own net, and the goalkeeper just managed to divert the ball over the bar to save his defender from humiliation.
Barcelona came out after the break with a new commitment to sending men forward, and it almost paid off just four minutes into the second period. David Villa did well to divert a rapid cross from Adriano on the way to the net, but Tono reacted just as quickly to save down low and keep the score level.
With 25 minutes to play, Messi was once again foiled. The Argentina captain first saw a volley taken away from him courtesy of more brave defending from Siqueira, before breaking clean through just minutes later to face Tono. 'La Pulga' looked destined to score, but the goalkeeper guessed right and denied Messi with a one-handed stop when Barcelona fans were already celebrating 1-0.
Barcelona kept searching for the deadlock breaker, but they were given no inch by a Granada team determined to take at least a point back to Andalucia. Sanchez was the next man to be denied by Tono as he steamed through with 15 minutes left, before Fabregas was left with his head in his hands having seen a golden chance fly wide of the post.
Granada looked set to withstand a late onslaught and take something from the encounter, but there was to be a cruel sting in the tail for the visitors.
With just four minutes left of regulation time, a deflected cross landed square at the feet of Xavi. The substitute took his time before releasing a wicked volley, which bounded in off the crossbar leaving the heroic Tono with absolutely no chance.
There was to be one more twist: deep in injury time, Messi's cross was turned into his own net by Gomez to put a revival out of Granada's reach.