Plumbing problem

[Jeremiah Jordan]

Last night I planned on replacing the spout on the tub at my residence (easy job right lol) and after taking the old spout off I realized that the galvanized 1/2" nipple sticking out of the wall was badly corroded and figured I would replace that as well. I went and got an inside pipe wrench to extract the nipple and as i started turning it it wouldn't grab and just started grinding the inside of the pipe out. I am assuming the pipe is badly corroded which is why I can't get the wrench to bite. Is there any other way I could extract the nipple without cutting a hole in the drywall behind that wall and doing it from inside the wall?