The district court abused its discretion in excluding testimony from defendant’s sole trial witness and in imposing monetary sanctions for defendants’ purported failure to properly identify the areas of testimony of the witness–who had been identified in the defendant’s initial disclosures. Even if the initial disclosures showed only that the witness would testify about the underlying lawsuit for which the defendants sought insurance coverage, not the coverage action itself, the nondisclosure was harmless as the plaintiff sued only for declaratory relief regarding coverage and the witness was the only one disclosed. The district court also erred in imposing sanctions without first determining whether the non-compliance with initial disclosure requirements involved willfulness, bad faith or fault.