Have the backsplash cut in one piece of marble or granite by an expert ..then you can cover it all and patch , BUT if you want to install tiles ,.then you need to strip it down and start over .

It ain't that bad. Scrape the mastic and patch. It'll be fine and faster than replacement.

This is pretty normal when you remove tile from drywall. I had this a few years ago and the tile installer easily cut out all the old drywall and put new in. You have to be sure to have a completely flat surface to install the new tile to and you’re not going to get that with a patch job.

Better to remove and replace the drywall. Cut a line through the drywall at the top and bottom with a drywall saw or knife, and then you can use a hammer to break the drywall into pieces and remove.

Repace the drywall I don’t know about ever getting that clean enough to install tile

My wall was like that and I put a patch over the one area that had a significant hole and just went over the rest with mastic. It was fine and the tile I installed went on great. I did go with a smaller tile size (4'' x 4'') because it's more forgiving with uneven walls. If you're going with a larger tile you might want to go down to the studs and start from scratch to get the flattest surface.

I’ve been doing remodels for 30 years. Just scrape off the high spots, cover with a layer durarock and tile. Don’t forget to bring the electric boxes forward.

I would want a fresh start on that wall....remove all the old lumpy stuff and start over. Before you get in there with sharp tools, I would turn off the power in that wall just to be safe. You will have a better new tile job if you start with a good subsurface. Yes, it may cost a bit more. If you are capable of a truly vertical repair job, go ahead. If you have any hesitation about your abilities, hire an experienced subcontractor.

When my 21 year old backsplash tile was demoed earlier this year, that's exactly what my drywall looked like. The tile did not come off easily at all. It was easier for the tile guy to cut out the drywall and replace it than try to patch it. That way it was guaranteed that he had a smooth surface to work with.

Thanks for the suggestions everyone. Looks like new drywall is the overwhelming suggestion. Will just go with that. Anything to watch out for while doing this?

My wall looked like that. It was patched, skim-coated and then tiled. Perfect.

Actually, I'm in the patch it, it'll be fine camp, but if you're putting in new drywall you might want to cover your hvac vents. The dust goes everywhere.

Patch and skim. I’ve seen way worse. But definitely use small tile. Not a bunch of dated mosaic. A mini subway, maybe.

I would replace. Patch and skim will work, but will take far more time than simply cutting out and replacing.