86In order to determine whether an undertaking is a potential competitor in a market, the Commission is required to determine whether, if the agreement at issue had not applied, there would have been real concrete possibilities for it to enter that market and to compete with established undertakings. Such a demonstration must not be based on a mere hypothesis, but must be supported by evidence or an analysis of the structures of the relevant market. Accordingly, an undertaking cannot be described as a potential competitor if its entry into a market is not an economically viable strategy (see, to that effect, Visa Europe and Visa International Service v Commission, paragraph 85 above, paragraphs 166 and 167).