The home side were ahead in the early stages of the second period when Xavi converted from close range, before Sanchez scored his second after 64 minutes.
Sanchez then turned provider after 70 minutes when he fed Neymar for their fourth of the match as Barcelona wrapped up the points in style.
Here, Sports Mole dissects the 90 minutes of action between the two Spanish rivals.
On target: 8
On target: 1
Was the result fair?
Barcelona certainly deserved to pick up all three points this evening, but the 4-1 scoreline is slightly harsh on Valladolid, who were in the match for long spells. The away side managed to hold the league leaders at the interval, but the Catalan outfit moved up another gear in the second period as they continued their incredible start to the season.
Another four goals for the home side as they continue to find the back of the net for fun. However, their defensive problems remain. Granted, it was only an isolated incident in this match as Guerra headed Valladolid into the lead following poor defending from a set piece, but it has happened all too often this season. That said, the likes of Neymar and Sanchez were both stunning this evening as Barcelona demonstrated that they can cope without a certain Lionel Messi.
Valladolid can be pleased with their overall level of performance this evening, but the four goals conceded have not done their goal difference any favours. They more than matched Barcelona in the opening 45 minutes, but simply could not match the home side in the second period. In truth, how they fare this season will not depend on their results at grounds such as Camp Nou.
Sports Mole's man of the match
Alexis Sanchez: The Chilean has been in fine form in the early part of the campaign and he continued that level of performance with a double this evening. His first, which brought his side level, was a stunning strike from outside the box, while his second demonstrated his finishing ability in close quarters. He also showed his unselfishness late on as he fed Neymar for Barcelona's third rather than attempt to complete his hat-trick.
Biggest gaffe of the match
Overall, it was another pleasing night for Barcelona, but they still have problems in defence. Those problems were demonstrated after 10 minutes when Guerra was allowed a free header inside the box after terrible marking from the home side. It is certainly something that needs to be addressed as the season gathers pace.
Jesus Gil had a fairly eventful first period as he twice denied Neymar a penalty even though it appeared that the Brazilian had been brought down inside the box on both occasions. Neymar had another shout in the second half, but still the referee was not interested. Aside from those isolated incidents, neither manager will have had too many complaints about his general work this evening.
Barcelona: The Catalan outfit will attempt to make it nine straight wins in the league when they travel to Osasuna on October 19.
Valladolid: Valladolid are next in La Liga action one day later as they welcome Sevilla on October 20.