Villa were ragged and when Matty Cash stumbled over the ball Christopher Nkunku rolled the ball to Fernandez who curled his shot over Martinez and onto the roof of the Villa net.
He managed to dig the ball back across goal and, though it fell behind Asensio, the Spaniard somehow managed to claw the ball back and screw it across the line.
And when he took out Martinez and Mings with a low cut back, Enzo Fernandez came steaming in to knock the ball into the empty net from close range for his fourth goal of the season.
He wriggled free in the Villa penalty area after three minutes but his shot was desperately blocked by Tyrone Mings who slid in to block.
It took Villa almost 20 minutes to show any threat at all as Filip Jorgensen reacted instinctively to block Ollie Watkins shot with his legs.
