Barca drops hammer on Valladolid
Valladolid had not won away since February but they stunned the Nou Camp by taking a 10th-minute lead through Javi Guerra's glancing header from a corner.
That was the first time Barcelona had trailed in La Liga or Europe this season but they were behind for just four minutes before Alexis Sanchez drew them level with a thunderous shot.
Xavi, Alexis and Neymar then added second-half goals as dominant Barca made it eight wins from eight in the league and open up a three-point lead over Atletico Madrid, who host Celta Vigo on Sunday.
With the likes of Lionel Messi, Carles Puyol and Javier Mascherano out injured, and Spain trio Andres Iniesta, Pedro Rodriguez and Sergio Busquets only on the bench, Valladolid might have felt a first win at the Nou Camp since 1997 could be within their capabilities.
And that briefly seemed a possibility when Guerra rose above Adriano to head Patrick Ebert's corner past Victor Valdes.
However, Valladolid barely had any time to enjoy being ahead against the Spanish champions before Barca equalised with an unstoppable rising strike from Alexis from outside the box.
After that it was pretty much all Barca and the only real surprise was that it took them so long to go ahead.
Visiting goalkeeper Diego Marino did well to keep out Neymar's shot with his feet before the break but there was no denying Xavi in the 52nd minute as the veteran playmaker side-footed home Cristian Tello's pass from near the penalty spot.
Tello then saw a spectacular 25-yard shot crash against the bar as Barca sought a third goal, which duly arrived in clinical fashion in the 63rd minute.
Xavi robbed Valladolid of the ball on the halfway before immediately feeding Neymar on the edge of the visiting side's box, and the Brazilian then laid the ball off into Alexis' path for the Chile winger to roll a first-time shot under Marino.
Alexis might have been celebrating a hat-trick in the 70th minute but, instead of shooting with only Marino to beat when eight yards out, he opted to lay the ball inside to Neymar, who took a touch before slotting home Barca's fourth of the night to complete the scoring.
''Neymar didn't put on a Messi mask, each one plays his own game,'' Alexis told GOL TV. ''I don't think that the fact Messi isn't here gives us more freedom. Without Leo we have more work because with him everything is easier.''