Deutscher's expertise in granular and disordered materials proved invaluable when high-temperature superconductivity was discovered in the late 1980s. He co-authored one of the most cited papers in the field with K. Alex Müller, the Nobel laureate who discovered the cuprate superconductors. This paper explored the relationship between the unique properties of high-temperature superconductivity and the inherent disorder in these materials. Deutscher's insight into the short coherence length of cuprates led to the first accepted explanation for the low critical current in ceramic and polycrystalline samples of these materials.