Context. Galaxy clusters are some of largest structures in the universe. These very dense environments tend to be home to higher numbers of evolved galaxies than found in lower-density environments. It is well known that dense environments can influence the evolution of galaxies through the removal of the neutral gas (H  I ) reservoirs that fuel star formation. It is unclear which environment has a stronger effect: the local environment (i.e., the substructure within the cluster), or the cluster itself. Aims. Using the new H  I data from the Westerbork Coma Survey, we explore the average H  I content of galaxies across the cluster comparing galaxies that reside in substructure to those that do not. Methods. We applied the Dressler–Shectman test to our newly compiled redshift catalogue of the Coma cluster to search for substructure. With so few of the Coma galaxies directly detected in H  I , we used the H  I stacking technique to probe the average H  I content below what can be directly detected. Results. Using the Dressler–Shectman test, we find 15 substructures within the footprint of the Westerbork Coma Survey. We compare the average H  I content for galaxies within substructure to those not in substructure. Using the H  I stacking technique, we find that those Coma galaxies not detected in H  I are more than 10–50 times more H  I deficient than expected, which supports the scenario of an extremely efficient and rapid quenching mechanism. By studying the galaxies that are not directly detected in H  I , we also find Coma to be more H  I deficient than previously thought.