An integrated inventory system has different sources which are uncertain in nature thus rendering the system and its outcome with a high uncertainty. Thus, implementing fuzzy reasoning in inventory modelling is essential to manage uncertainties. This study has developed a model that deals with the production and replenishment co-ordination in a three-echelon supply chain involving two manufacturers and a retailer with fuzzy parameters formulated as triangular fuzzy numbers. The model is thus designed in a way that verifies the unreliable nature of the production process and segregates the defective products from the perfect products. The defective products are routed to another market where they can be sold at a reduced price while the perfect products reach the manufacturer and in turn, the retailer. In today’s scenario, it has become vital to incorporate green activities into supply chain management. Here the study provided an end of life treatment of the retired products and the reverse flow of products has been considered as the responsibility of the manufacturer. The model considers the costs of idle times at the end of both manufacturers. It is a general model that can be a useful equipment for any kind of product but to show its practicability, we have introduced the example of the tennis racket. It is demonstrated by the numerical examples that the collection of the buyback products is lucrative for the system and the vagueness in the demand parameter affects the most to the optimality instead of other parameters. Other managerial insights are also provided.