I don't think anyone ever considered Joel Skinner a can't-miss prospect. He was a 37th-round draft pick from the Pirates system and never hit consistently in the minors before never hitting consistently in the majors, although he was regarded as a pretty good defensive catcher. Ron Karkovice, who came up late in the 1986 season, was the first-round pick who seemed to be developing into a solid hitter.
I recall reading that Harrelson said the idea of moving Fisk to left was to extend his career, not to find a place for Skinner to play every day or that the Sox needed to make room for Karkovice. In fact, Skinner was traded midway through the 1986 season. I don't think the White Sox really looked at catchers as being key to the offense between Fisk and Pierzynski.