Could a herniated disk without nerve compression still cause sciatica pain?

Sciatica= nerve com-: Pression of the nerves making the sciatic nerve. If no compression then sciatica is unlikely, except if the compression is by spurs of bone from arthritis or thickened l flavum or some other lesion after nerve has exited out of the spine.

Annular tear: Sometimes the herniated disk has annular tear that releases the spongier nucleus pulposus out that can cause a chemical neuritis on the nerves that is similar to sciatica. Also if the MRI reflects any listhesis (slipping of one bone on the other) there may be a compression on the nerves that will not be appreciated on the MRI because you are lying down and not allowing gravity/forces to move it.