Each of the small fireballs is countered by bolts of deeper red striking them from the sky before they can touch the Arrancar. He gets directly behind the beast just as the greater blast is launched. The beast doesn't see what happens next as the vermillion blast obscures him from sight. When it comes to a stop, it might notice the flame is still continuing its way up to the sky - but there's no trace of the Arrancar, not even faintest hint of his presence - it's as if he's vanished from the face of earth.