In antitrust suits, one of the most commonly overlooked requirements is "standing," which refers to the validity of the plaintiff's grounds for bringing the lawsuit. In other words, the plaintiff must have suffered an antitrust injury, or suffered damages due to a defendant's anticompetitive conduct. The damages must be of the nature that the antitrust laws were designed to prevent. There must also be a causal link between the damages and the anticompetitive conduct.
It is relatively frequent in everyday business to suffer detriment in connection with other companies' anticompetitive conduct. But the anticompetitive conduct is not always the direct cause of the damages. The detriment to the plaintiff is not always of the nature that the antitrust laws were designed to prevent. So, if you lack the causal link, you cannot bring an antitrust suit even if you are damaged. There may be other grounds on which you can bring suit, but you would not be able to do so on an antitrust theory.