Override animation in LateUpdate()

Hi, I want to make a Mech's head look at the player, the Mech is animated so to use ..

 transform.LookAt (_player.transform.position);

in LateUpdate() works fine but I want to slowly rotate it to it's position but using ..

 transform.rotation = Quaternion.Slerp(transform.rotation, (Quaternion.LookRotation(transform.position - _player.transform.position)), Time.deltaTime * _rotationTime);

does not work in LateUpdate() .. Is there a way to override the animation slowly rotating?

Thanks.