The Blaugrana are 11 points clear at the top of La Liga ahead of their match against Sociedad on Saturday, having dropped just two points throughout the campaign.
"Nobody really knows what to do in order to stop Barcelona. If anybody knew, they would already have been beaten," Goal.com quotes Vela as saying.
"We will just try to play our own game, and hope we will see enough of the ball. We might be able to get something from this game if they have a bad day.
"If they're on top of their game, it will be impossible for us to record a good result, though."
Barcelona beat Sociedad 5-1 at the Camp Nou earlier this season.